path: root/doc/generated/functions.gen

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sconsdoc [
    <!ENTITY % scons SYSTEM "../scons.mod">
    %scons;
    <!ENTITY % builders-mod SYSTEM "builders.mod">
    %builders-mod;
    <!ENTITY % functions-mod SYSTEM "functions.mod">
    %functions-mod;
    <!ENTITY % tools-mod SYSTEM "tools.mod">
    %tools-mod;
    <!ENTITY % variables-mod SYSTEM "variables.mod">
    %variables-mod;
]>

<variablelist xmlns="http://www.scons.org/dbxsd/v1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.scons.org/dbxsd/v1.0 http://www.scons.org/dbxsd/v1.0/scons.xsd">
  <varlistentry id="f-Action">
    <term>
      <literal>Action(action, [cmd/str/fun, [var, ...]] [option=value, ...])</literal>
    </term>
    <term>
      <literal>env.Action(action, [cmd/str/fun, [var, ...]] [option=value, ...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Creates an Action object for
the specified
<varname>action</varname>.
See the section "Action Objects,"
below, for a complete explanation of the arguments and behavior.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that the
<function>env.Action</function>()
form of the invocation will expand
construction variables in any argument strings,
including the
<varname>action</varname>
argument, at the time it is called
using the construction variables in the
<varname>env</varname>
construction environment through which
<function>env.Action</function>()
was called.
The
<function>Action</function>()
form delays all variable expansion
until the Action object is actually used.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-AddMethod">
    <term>
      <literal>AddMethod(object, function, [name])</literal>
    </term>
    <term>
      <literal>env.AddMethod(function, [name])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
When called with the
<function>AddMethod</function>()
form,
adds the specified
<varname>function</varname>
to the specified
<varname>object</varname>
as the specified method
<varname>name</varname>.
When called with the
<function>env.AddMethod</function>()
form,
adds the specified
<varname>function</varname>
to the construction environment
<varname>env</varname>
as the specified method
<varname>name</varname>.
In both cases, if
<varname>name</varname>
is omitted or
<literal>None</literal>,
the name of the
specified
<varname>function</varname>
itself is used for the method name.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# Note that the first argument to the function to
# be attached as a method must be the object through
# which the method will be called; the Python
# convention is to call it 'self'.
def my_method(self, arg):
    print("my_method() got", arg)

# Use the global AddMethod() function to add a method
# to the Environment class.  This
AddMethod(Environment, my_method)
env = Environment()
env.my_method('arg')

# Add the function as a method, using the function
# name for the method call.
env = Environment()
env.AddMethod(my_method, 'other_method_name')
env.other_method_name('another arg')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-AddOption">
    <term>
      <literal>AddOption(arguments)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This function adds a new command-line option to be recognized.
The specified
<varname>arguments</varname>
are the same as supported by the standard Python
<function>optparse.add_option</function>()
method (with a few additional capabilities noted below);
see the documentation for
<literal>optparse</literal>
for a thorough discussion of its option-processing capabities.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
In addition to the arguments and values supported by the
<function>optparse.add_option</function>()
method,
the SCons
<function xmlns="http://www.scons.org/dbxsd/v1.0">AddOption</function>
function allows you to set the
<literal>nargs</literal>
keyword value to
<literal>'?'</literal>
(a string with just the question mark)
to indicate that the specified long option(s) take(s) an
<emphasis>optional</emphasis>
argument.
When
<literal>nargs = '?'</literal>
is passed to the
<function xmlns="http://www.scons.org/dbxsd/v1.0">AddOption</function>
function, the
<literal>const</literal>
keyword argument
may be used to supply the "default"
value that should be used when the
option is specified on the command line
without an explicit argument.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If no
<literal>default=</literal>
keyword argument is supplied when calling
<function xmlns="http://www.scons.org/dbxsd/v1.0">AddOption</function>,
the option will have a default value of
<literal>None</literal>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Once a new command-line option has been added with
<function xmlns="http://www.scons.org/dbxsd/v1.0">AddOption</function>,
the option value may be accessed using
<function xmlns="http://www.scons.org/dbxsd/v1.0">GetOption</function>
or
<function>env.GetOption</function>().
The value may also be set, using
<function xmlns="http://www.scons.org/dbxsd/v1.0">SetOption</function>
or
<function>env.SetOption</function>(),
if conditions in a
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
require overriding any default value.
Note, however, that a
value specified on the command line will
<emphasis>always</emphasis>
override a value set by any SConscript file.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Any specified
<literal>help=</literal>
strings for the new option(s)
will be displayed by the
<option>-H</option>
or
<option>-h</option>
options
(the latter only if no other help text is
specified in the SConscript files).
The help text for the local options specified by
<function xmlns="http://www.scons.org/dbxsd/v1.0">AddOption</function>
will appear below the SCons options themselves,
under a separate
<literal>Local Options</literal>
heading.
The options will appear in the help text
in the order in which the
<function xmlns="http://www.scons.org/dbxsd/v1.0">AddOption</function>
calls occur.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
AddOption('--prefix',
          dest='prefix',
          nargs=1, type='string',
          action='store',
          metavar='DIR',
          help='installation prefix')
env = Environment(PREFIX = GetOption('prefix'))
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-AddPostAction">
    <term>
      <literal>AddPostAction(target, action)</literal>
    </term>
    <term>
      <literal>env.AddPostAction(target, action)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Arranges for the specified
<varname>action</varname>
to be performed
after the specified
<varname>target</varname>
has been built.
The specified action(s) may be
an Action object, or anything that
can be converted into an Action object
(see below).
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
When multiple targets are supplied,
the action may be called multiple times,
once after each action that generates
one or more targets in the list.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-AddPreAction">
    <term>
      <literal>AddPreAction(target, action)</literal>
    </term>
    <term>
      <literal>env.AddPreAction(target, action)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Arranges for the specified
<varname>action</varname>
to be performed
before the specified
<varname>target</varname>
is built.
The specified action(s) may be
an Action object, or anything that
can be converted into an Action object
(see below).
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
When multiple targets are specified,
the action(s) may be called multiple times,
once before each action that generates
one or more targets in the list.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that if any of the targets are built in multiple steps,
the action will be invoked just
before the "final" action that specifically
generates the specified target(s).
For example, when building an executable program
from a specified source
<filename>.c</filename>
file via an intermediate object file:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
foo = Program('foo.c')
AddPreAction(foo, 'pre_action')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The specified
<literal>pre_action</literal>
would be executed before
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
calls the link command that actually
generates the executable program binary
<filename>foo</filename>,
not before compiling the
<filename>foo.c</filename>
file into an object file.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Alias">
    <term>
      <literal>Alias(alias, [targets, [action]])</literal>
    </term>
    <term>
      <literal>env.Alias(alias, [targets, [action]])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Creates one or more phony targets that
expand to one or more other targets.
An optional
<varname>action</varname>
(command)
or list of actions
can be specified that will be executed
whenever the any of the alias targets are out-of-date.
Returns the Node object representing the alias,
which exists outside of any file system.
This Node object, or the alias name,
may be used as a dependency of any other target,
including another alias.
<function xmlns="http://www.scons.org/dbxsd/v1.0">Alias</function>
can be called multiple times for the same
alias to add additional targets to the alias,
or additional actions to the list for this alias.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Alias('install')
Alias('install', '/usr/bin')
Alias(['install', 'install-lib'], '/usr/local/lib')

env.Alias('install', ['/usr/local/bin', '/usr/local/lib'])
env.Alias('install', ['/usr/local/man'])

env.Alias('update', ['file1', 'file2'], "update_database $SOURCES")
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-AllowSubstExceptions">
    <term>
      <literal>AllowSubstExceptions([exception, ...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies the exceptions that will be allowed
when expanding construction variables.
By default,
any construction variable expansions that generate a
<literal>NameError</literal>
or
<literal>IndexError</literal>
exception will expand to a
<literal>''</literal>
(a null string) and not cause scons to fail.
All exceptions not in the specified list
will generate an error message
and terminate processing.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<function xmlns="http://www.scons.org/dbxsd/v1.0">AllowSubstExceptions</function>
is called multiple times,
each call completely overwrites the previous list
of allowed exceptions.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# Requires that all construction variable names exist.
# (You may wish to do this if you want to enforce strictly
# that all construction variables must be defined before use.)
AllowSubstExceptions()

# Also allow a string containing a zero-division expansion
# like '${1 / 0}' to evalute to ''.
AllowSubstExceptions(IndexError, NameError, ZeroDivisionError)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-AlwaysBuild">
    <term>
      <literal>AlwaysBuild(target, ...)</literal>
    </term>
    <term>
      <literal>env.AlwaysBuild(target, ...)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Marks each given
<varname>target</varname>
so that it is always assumed to be out of date,
and will always be rebuilt if needed.
Note, however, that
<function xmlns="http://www.scons.org/dbxsd/v1.0">AlwaysBuild</function>
does not add its target(s) to the default target list,
so the targets will only be built
if they are specified on the command line,
or are a dependent of a target specified on the command line--but
they will
<emphasis>always</emphasis>
be built if so specified.
Multiple targets can be passed in to a single call to
<function xmlns="http://www.scons.org/dbxsd/v1.0">AlwaysBuild</function>.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Append">
    <term>
      <literal>env.Append(key=val, [...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Appends the specified keyword arguments
to the end of construction variables in the environment.
If the Environment does not have
the specified construction variable,
it is simply added to the environment.
If the values of the construction variable
and the keyword argument are the same type,
then the two values will be simply added together.
Otherwise, the construction variable
and the value of the keyword argument
are both coerced to lists,
and the lists are added together.
(See also the Prepend method, below.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Append(CCFLAGS = ' -g', FOO = ['foo.yyy'])
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-AppendENVPath">
    <term>
      <literal>env.AppendENVPath(name, newpath, [envname, sep, delete_existing])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This appends new path elements to the given path in the
specified external environment
(<literal>ENV</literal>
by default).
This will only add
any particular path once (leaving the last one it encounters and
ignoring the rest, to preserve path order),
and to help assure this,
will normalize all paths (using
<function>os.path.normpath</function>
and
<function>os.path.normcase</function>).
This can also handle the
case where the given old path variable is a list instead of a
string, in which case a list will be returned instead of a string.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<varname>delete_existing</varname>
is 0, then adding a path that already exists
will not move it to the end; it will stay where it is in the list.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
print 'before:',env['ENV']['INCLUDE']
include_path = '/foo/bar:/foo'
env.AppendENVPath('INCLUDE', include_path)
print 'after:',env['ENV']['INCLUDE']

yields:
before: /foo:/biz
after: /biz:/foo/bar:/foo
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-AppendUnique">
    <term>
      <literal>env.AppendUnique(key=val, [...], delete_existing=0)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Appends the specified keyword arguments
to the end of construction variables in the environment.
If the Environment does not have
the specified construction variable,
it is simply added to the environment.
If the construction variable being appended to is a list,
then any value(s) that already exist in the
construction variable will
<emphasis>not</emphasis>
be added again to the list.
However, if delete_existing is 1,
existing matching values are removed first, so
existing values in the arg list move to the end of the list.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.AppendUnique(CCFLAGS = '-g', FOO = ['foo.yyy'])
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-BuildDir">
    <term>
      <literal>BuildDir(build_dir, src_dir, [duplicate])</literal>
    </term>
    <term>
      <literal>env.BuildDir(build_dir, src_dir, [duplicate])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Deprecated synonyms for
<function xmlns="http://www.scons.org/dbxsd/v1.0">VariantDir</function>
and
<function>env.VariantDir</function>().
The
<varname>build_dir</varname>
argument becomes the
<varname>variant_dir</varname>
argument of
<function xmlns="http://www.scons.org/dbxsd/v1.0">VariantDir</function>
or
<function>env.VariantDir</function>().
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Builder">
    <term>
      <literal>Builder(action, [arguments])</literal>
    </term>
    <term>
      <literal>env.Builder(action, [arguments])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Creates a Builder object for
the specified
<varname>action</varname>.
See the section "Builder Objects,"
below, for a complete explanation of the arguments and behavior.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that the
<function>env.Builder</function>()
form of the invocation will expand
construction variables in any arguments strings,
including the
<varname>action</varname>
argument,
at the time it is called
using the construction variables in the
<varname>env</varname>
construction environment through which
<function>env.Builder</function>()
was called.
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">Builder</function>
form delays all variable expansion
until after the Builder object is actually called.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-CacheDir">
    <term>
      <literal>CacheDir(cache_dir)</literal>
    </term>
    <term>
      <literal>env.CacheDir(cache_dir)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies that
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will maintain a cache of derived files in
<varname>cache_dir</varname>.
The derived files in the cache will be shared
among all the builds using the same
<function xmlns="http://www.scons.org/dbxsd/v1.0">CacheDir</function>
call.
Specifying a
<varname>cache_dir</varname>
of
<literal>None</literal>
disables derived file caching.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Calling
<function>env.CacheDir</function>()
will only affect targets built
through the specified construction environment.
Calling
<function xmlns="http://www.scons.org/dbxsd/v1.0">CacheDir</function>
sets a global default
that will be used by all targets built
through construction environments
that do
<emphasis>not</emphasis>
have an
<function>env.CacheDir</function>()
specified.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
When a
<function>CacheDir</function>()
is being used and
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
finds a derived file that needs to be rebuilt,
it will first look in the cache to see if a
derived file has already been built
from identical input files and an identical build action
(as incorporated into the MD5 build signature).
If so,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will retrieve the file from the cache.
If the derived file is not present in the cache,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will rebuild it and
then place a copy of the built file in the cache
(identified by its MD5 build signature),
so that it may be retrieved by other
builds that need to build the same derived file
from identical inputs.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Use of a specified
<function xmlns="http://www.scons.org/dbxsd/v1.0">CacheDir</function>
may be disabled for any invocation
by using the
<option>--cache-disable</option>
option.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the
<option>--cache-force</option>
option is used,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will place a copy of
<emphasis>all</emphasis>
derived files in the cache,
even if they already existed
and were not built by this invocation.
This is useful to populate a cache
the first time
<function xmlns="http://www.scons.org/dbxsd/v1.0">CacheDir</function>
is added to a build,
or after using the
<option>--cache-disable</option>
option.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
When using
<function xmlns="http://www.scons.org/dbxsd/v1.0">CacheDir</function>,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will report,
"Retrieved `file' from cache,"
unless the
<option>--cache-show</option>
option is being used.
When the
<option>--cache-show</option>
option is used,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will print the action that
<emphasis>would</emphasis>
have been used to build the file,
without any indication that
the file was actually retrieved from the cache.
This is useful to generate build logs
that are equivalent regardless of whether
a given derived file has been built in-place
or retrieved from the cache.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-NoCache"><function>NoCache</function></link>
method can be used to disable caching of specific files.  This can be
useful if inputs and/or outputs of some tool are impossible to
predict or prohibitively large.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Clean">
    <term>
      <literal>Clean(targets, files_or_dirs)</literal>
    </term>
    <term>
      <literal>env.Clean(targets, files_or_dirs)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This specifies a list of files or directories which should be removed
whenever the targets are specified with the
<option>-c</option>
command line option.
The specified targets may be a list
or an individual target.
Multiple calls to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Clean</function>
are legal,
and create new targets or add files and directories to the
clean list for the specified targets.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Multiple files or directories should be specified
either as separate arguments to the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Clean</function>
method, or as a list.
<function xmlns="http://www.scons.org/dbxsd/v1.0">Clean</function>
will also accept the return value of any of the construction environment
Builder methods.
Examples:
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The related
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-NoClean"><function>NoClean</function></link>
function overrides calling
<function xmlns="http://www.scons.org/dbxsd/v1.0">Clean</function>
for the same target,
and any targets passed to both functions will
<emphasis>not</emphasis>
be removed by the
<option>-c</option>
option.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Clean('foo', ['bar', 'baz'])
Clean('dist', env.Program('hello', 'hello.c'))
Clean(['foo', 'bar'], 'something_else_to_clean')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
In this example,
installing the project creates a subdirectory for the documentation.
This statement causes the subdirectory to be removed
if the project is deinstalled.
</para>
<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Clean(docdir, os.path.join(docdir, projectname))
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Clone">
    <term>
      <literal>env.Clone([key=val, ...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns a separate copy of a construction environment.
If there are any keyword arguments specified,
they are added to the returned copy,
overwriting any existing values
for the keywords.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env2 = env.Clone()
env3 = env.Clone(CCFLAGS = '-g')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Additionally, a list of tools and a toolpath may be specified, as in
the Environment constructor:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
def MyTool(env): env['FOO'] = 'bar'
env4 = env.Clone(tools = ['msvc', MyTool])
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<varname>parse_flags</varname>
keyword argument is also recognized to allow merging command-line
style arguments into the appropriate construction
variables (see <link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-MergeFlags"><function>env.MergeFlags</function></link>).
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# create an environment for compiling programs that use wxWidgets
wx_env = env.Clone(parse_flags='!wx-config --cflags --cxxflags')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Command">
    <term>
      <literal>Command(target, source, action, [key=val, ...])</literal>
    </term>
    <term>
      <literal>env.Command(target, source, action, [key=val, ...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Executes a specific action
(or list of actions)
to build a target file or files.
This is more convenient
than defining a separate Builder object
for a single special-case build.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
As a special case, the
<varname>source_scanner</varname>
keyword argument can
be used to specify
a Scanner object
that will be used to scan the sources.
(The global
<literal>DirScanner</literal>
object can be used
if any of the sources will be directories
that must be scanned on-disk for
changes to files that aren't
already specified in other Builder of function calls.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Any other keyword arguments specified override any
same-named existing construction variables.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
An action can be an external command,
specified as a string,
or a callable Python object;
see "Action Objects," below,
for more complete information.
Also note that a string specifying an external command
may be preceded by an
<literal>@</literal>
(at-sign)
to suppress printing the command in question,
or by a
<literal>-</literal>
(hyphen)
to ignore the exit status of the external command.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Command('foo.out', 'foo.in',
            "$FOO_BUILD &lt; $SOURCES &gt; $TARGET")

env.Command('bar.out', 'bar.in',
            ["rm -f $TARGET",
             "$BAR_BUILD &lt; $SOURCES &gt; $TARGET"],
            ENV = {'PATH' : '/usr/local/bin/'})

def rename(env, target, source):
    import os
    os.rename('.tmp', str(target[0]))

env.Command('baz.out', 'baz.in',
            ["$BAZ_BUILD &lt; $SOURCES &gt; .tmp",
	     rename ])
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Command</function>
function will usually assume, by default,
that the specified targets and/or sources are Files,
if no other part of the configuration
identifies what type of entry it is.
If necessary, you can explicitly specify
that targets or source nodes should
be treated as directoriese
by using the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Dir"><function>Dir</function></link>
or
<function>env.Dir</function>()
functions.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Command('ddd.list', Dir('ddd'), 'ls -l $SOURCE &gt; $TARGET')

env['DISTDIR'] = 'destination/directory'
env.Command(env.Dir('$DISTDIR')), None, make_distdir)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
(Also note that SCons will usually
automatically create any directory necessary to hold a target file,
so you normally don't need to create directories by hand.)
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Configure">
    <term>
      <literal>Configure(env, [custom_tests, conf_dir, log_file, config_h])</literal>
    </term>
    <term>
      <literal>env.Configure([custom_tests, conf_dir, log_file, config_h])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Creates a Configure object for integrated
functionality similar to GNU autoconf.
See the section "Configure Contexts,"
below, for a complete explanation of the arguments and behavior.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Copy">
    <term>
      <literal>env.Copy([key=val, ...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
A now-deprecated synonym for
<function>env.Clone</function>().
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Decider">
    <term>
      <literal>Decider(function)</literal>
    </term>
    <term>
      <literal>env.Decider(function)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies that all up-to-date decisions for
targets built through this construction environment
will be handled by the specified
<varname>function</varname>.
The
<varname>function</varname>
can be one of the following strings
that specify the type of decision function
to be performed:
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<variablelist>
<varlistentry>
<term><literal>timestamp-newer</literal></term>
<listitem>
<para>
Specifies that a target shall be considered out of date and rebuilt
if the dependency's timestamp is newer than the target file's timestamp.
This is the behavior of the classic Make utility,
and
<literal>make</literal>
can be used a synonym for
<literal>timestamp-newer</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>timestamp-match</literal></term>
<listitem>
<para>
Specifies that a target shall be considered out of date and rebuilt
if the dependency's timestamp is different than the
timestamp recorded the last time the target was built.
This provides behavior very similar to the classic Make utility
(in particular, files are not opened up so that their
contents can be checksummed)
except that the target will also be rebuilt if a
dependency file has been restored to a version with an
<emphasis>earlier</emphasis>
timestamp, such as can happen when restoring files from backup archives.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>MD5</literal></term>
<listitem>
<para>
Specifies that a target shall be considered out of date and rebuilt
if the dependency's content has changed since the last time
the target was built,
as determined be performing an MD5 checksum
on the dependency's contents
and comparing it to the checksum recorded the
last time the target was built.
<literal>content</literal>
can be used as a synonym for
<literal>MD5</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>MD5-timestamp</literal></term>
<listitem>
<para>
Specifies that a target shall be considered out of date and rebuilt
if the dependency's content has changed since the last time
the target was built,
except that dependencies with a timestamp that matches
the last time the target was rebuilt will be
assumed to be up-to-date and
<emphasis>not</emphasis>
rebuilt.
This provides behavior very similar
to the
<literal>MD5</literal>
behavior of always checksumming file contents,
with an optimization of not checking
the contents of files whose timestamps haven't changed.
The drawback is that SCons will
<emphasis>not</emphasis>
detect if a file's content has changed
but its timestamp is the same,
as might happen in an automated script
that runs a build,
updates a file,
and runs the build again,
all within a single second.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# Use exact timestamp matches by default.
Decider('timestamp-match')

# Use MD5 content signatures for any targets built
# with the attached construction environment.
env.Decider('content')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
In addition to the above already-available functions,
the
<varname>function</varname>
argument may be an actual Python function
that takes the following three arguments:
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<variablelist>
<varlistentry>
<term><parameter>dependency</parameter></term>
<listitem>
<para>
The Node (file) which
should cause the
<varname>target</varname>
to be rebuilt
if it has "changed" since the last tme
<varname>target</varname>
was built.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>target</parameter></term>
<listitem>
<para>
The Node (file) being built.
In the normal case,
this is what should get rebuilt
if the
<varname>dependency</varname>
has "changed."
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>prev_ni</parameter></term>
<listitem>
<para>
Stored information about the state of the
<varname>dependency</varname>
the last time the
<varname>target</varname>
was built.
This can be consulted to match various
file characteristics
such as the timestamp,
size, or content signature.
</para>
</listitem>
</varlistentry>
    <varlistentry>
<term><parameter>repo_node</parameter></term>
<listitem>
<para>
Use this node instead of the one specified by
<varname>dependency</varname>
    to determine if the dependency has changed.
</para>
</listitem>
</varlistentry>

</variablelist>
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<varname>function</varname>
should return a
<literal>True</literal>
(non-zero)
value if the
<varname>dependency</varname>
has "changed" since the last time
the
<varname>target</varname>
was built
(indicating that the target
<emphasis>should</emphasis>
be rebuilt),
and
<literal>False</literal>
(zero)
otherwise
(indicating that the target should
<emphasis>not</emphasis>
be rebuilt).
Note that the decision can be made
using whatever criteria are appopriate.
Ignoring some or all of the function arguments
is perfectly normal.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
def my_decider(dependency, target, prev_ni, repo_node=None):
    return not os.path.exists(str(target))

env.Decider(my_decider)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Default">
    <term>
      <literal>Default(targets)</literal>
    </term>
    <term>
      <literal>env.Default(targets)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This specifies a list of default targets,
which will be built by
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
if no explicit targets are given on the command line.
Multiple calls to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Default</function>
are legal,
and add to the list of default targets.
As noted above, both forms of this call affect the
same global list of default targets; the
construction environment method applies
construction variable expansion to the targets.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Multiple targets should be specified as
separate arguments to the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Default</function>
method, or as a list.
<function xmlns="http://www.scons.org/dbxsd/v1.0">Default</function>
will also accept the Node returned by any
of a construction environment's
builder methods.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Default('foo', 'bar', 'baz')
env.Default(['a', 'b', 'c'])
hello = env.Program('hello', 'hello.c')
env.Default(hello)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
An argument to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Default</function>
of
<literal>None</literal>
will clear all default targets.
Later calls to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Default</function>
will add to the (now empty) default-target list
like normal.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The current list of targets added using the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Default</function>
function or method is available in the
<literal>DEFAULT_TARGETS</literal>
list;
see below.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-DefaultEnvironment">
    <term>
      <literal>DefaultEnvironment([args])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Creates and returns a default construction environment object.
This construction environment is used internally by SCons
in order to execute many of the global functions in this list,
and to fetch source files transparently
from source code management systems.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Depends">
    <term>
      <literal>Depends(target, dependency)</literal>
    </term>
    <term>
      <literal>env.Depends(target, dependency)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies an explicit dependency;
the
<varname>target</varname>
will be rebuilt
whenever the
<varname>dependency</varname>
has changed.
Both the specified
<varname>target</varname>
and
<varname>dependency</varname>
can be a string
(usually the path name of a file or directory)
or Node objects,
or a list of strings or Node objects
(such as returned by a Builder call).
This should only be necessary
for cases where the dependency
is not caught by a Scanner
for the file.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Depends('foo', 'other-input-file-for-foo')

mylib = env.Library('mylib.c')
installed_lib = env.Install('lib', mylib)
bar = env.Program('bar.c')

# Arrange for the library to be copied into the installation
# directory before trying to build the "bar" program.
# (Note that this is for example only.  A "real" library
# dependency would normally be configured through the $LIBS
# and $LIBPATH variables, not using an env.Depends() call.)

env.Depends(bar, installed_lib)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Dictionary">
    <term>
      <literal>env.Dictionary([vars])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns a dictionary object
containing copies of all of the
construction variables in the environment.
If there are any variable names specified,
only the specified construction
variables are returned in the dictionary.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
dict = env.Dictionary()
cc_dict = env.Dictionary('CC', 'CCFLAGS', 'CCCOM')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Dir">
    <term>
      <literal>Dir(name, [directory])</literal>
    </term>
    <term>
      <literal>env.Dir(name, [directory])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This returns a Directory Node,
an object that represents the specified directory
<varname>name</varname>.
<varname>name</varname>
can be a relative or absolute path.
<varname>directory</varname>
is an optional directory that will be used as the parent directory.
If no
<varname>directory</varname>
is specified, the current script's directory is used as the parent.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<varname>name</varname>
is a list, SCons returns a list of Dir nodes.
Construction variables are expanded in
<varname>name</varname>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Directory Nodes can be used anywhere you
would supply a string as a directory name
to a Builder method or function.
Directory Nodes have attributes and methods
that are useful in many situations;
see "File and Directory Nodes," below.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Dump">
    <term>
      <literal>env.Dump([key])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns a pretty printable representation of the environment.
<varname>key</varname>,
if not
<literal>None</literal>,
should be a string containing the name of the variable of interest.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
This SConstruct:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env=Environment()
print env.Dump('CCCOM')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
will print:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
'$CC -c -o $TARGET $CCFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS $SOURCES'
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
While this SConstruct:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env=Environment()
print env.Dump()
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
will print:
</para>
<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
{ 'AR': 'ar',
  'ARCOM': '$AR $ARFLAGS $TARGET $SOURCES\n$RANLIB $RANLIBFLAGS $TARGET',
  'ARFLAGS': ['r'],
  'AS': 'as',
  'ASCOM': '$AS $ASFLAGS -o $TARGET $SOURCES',
  'ASFLAGS': [],
  ...
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-EnsurePythonVersion">
    <term>
      <literal>EnsurePythonVersion(major, minor)</literal>
    </term>
    <term>
      <literal>env.EnsurePythonVersion(major, minor)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Ensure that the Python version is at least
<varname>major</varname>.<varname>minor</varname>.
This function will
print out an error message and exit SCons with a non-zero exit code if the
actual Python version is not late enough.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
EnsurePythonVersion(2,2)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-EnsureSConsVersion">
    <term>
      <literal>EnsureSConsVersion(major, minor, [revision])</literal>
    </term>
    <term>
      <literal>env.EnsureSConsVersion(major, minor, [revision])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Ensure that the SCons version is at least
<varname>major.minor</varname>,
or
<varname>major.minor.revision</varname>.
if
<varname>revision</varname>
is specified.
This function will
print out an error message and exit SCons with a non-zero exit code if the
actual SCons version is not late enough.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
EnsureSConsVersion(0,14)

EnsureSConsVersion(0,96,90)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Environment">
    <term>
      <literal>Environment([key=value, ...])</literal>
    </term>
    <term>
      <literal>env.Environment([key=value, ...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Return a new construction environment
initialized with the specified
<varname>key</varname><literal>=</literal><varname>value</varname>
pairs.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Execute">
    <term>
      <literal>Execute(action, [strfunction, varlist])</literal>
    </term>
    <term>
      <literal>env.Execute(action, [strfunction, varlist])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Executes an Action object.
The specified
<varname>action</varname>
may be an Action object
(see the section "Action Objects,"
below, for a complete explanation of the arguments and behavior),
or it may be a command-line string,
list of commands,
or executable Python function,
each of which will be converted
into an Action object
and then executed.
The exit value of the command
or return value of the Python function
will be returned.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will print an error message if the executed
<varname>action</varname>
fails--that is,
exits with or returns a non-zero value.
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will
<emphasis>not</emphasis>,
however,
automatically terminate the build
if the specified
<varname>action</varname>
fails.
If you want the build to stop in response to a failed
<function xmlns="http://www.scons.org/dbxsd/v1.0">Execute</function>
call,
you must explicitly check for a non-zero return value:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Execute(Copy('file.out', 'file.in'))

if Execute("mkdir sub/dir/ectory"):
    # The mkdir failed, don't try to build.
    Exit(1)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Exit">
    <term>
      <literal>Exit([value])</literal>
    </term>
    <term>
      <literal>env.Exit([value])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This tells
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to exit immediately
with the specified
<varname>value</varname>.
A default exit value of
<literal>0</literal>
(zero)
is used if no value is specified.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Export">
    <term>
      <literal>Export(vars)</literal>
    </term>
    <term>
      <literal>env.Export(vars)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This tells
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to export a list of variables from the current
SConscript file to all other SConscript files.
The exported variables are kept in a global collection,
so subsequent calls to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Export</function>
will over-write previous exports that have the same name.
Multiple variable names can be passed to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Export</function>
as separate arguments or as a list.
Keyword arguments can be used to provide names and their values.
A dictionary can be used to map variables to a different name when exported.
Both local variables and global variables can be exported.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env = Environment()
# Make env available for all SConscript files to Import().
Export("env")

package = 'my_name'
# Make env and package available for all SConscript files:.
Export("env", "package")

# Make env and package available for all SConscript files:
Export(["env", "package"])

# Make env available using the name debug:
Export(debug = env)

# Make env available using the name debug:
Export({"debug":env})
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that the
<function xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</function>
function supports an
<varname>exports</varname>
argument that makes it easier to to export a variable or
set of variables to a single SConscript file.
See the description of the
<function xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</function>
function, below.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-File">
    <term>
      <literal>File(name, [directory])</literal>
    </term>
    <term>
      <literal>env.File(name, [directory])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This returns a
File Node,
an object that represents the specified file
<varname>name</varname>.
<varname>name</varname>
can be a relative or absolute path.
<varname>directory</varname>
is an optional directory that will be used as the parent directory.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<varname>name</varname>
is a list, SCons returns a list of File nodes.
Construction variables are expanded in
<varname>name</varname>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
File Nodes can be used anywhere you
would supply a string as a file name
to a Builder method or function.
File Nodes have attributes and methods
that are useful in many situations;
see "File and Directory Nodes," below.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-FindFile">
    <term>
      <literal>FindFile(file, dirs)</literal>
    </term>
    <term>
      <literal>env.FindFile(file, dirs)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Search for
<varname>file</varname>
in the path specified by
<varname>dirs</varname>.
<varname>dirs</varname>
may be a list of directory names or a single directory name.
In addition to searching for files that exist in the filesystem,
this function also searches for derived files
that have not yet been built.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
foo = env.FindFile('foo', ['dir1', 'dir2'])
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-FindInstalledFiles">
    <term>
      <literal>FindInstalledFiles()</literal>
    </term>
    <term>
      <literal>env.FindInstalledFiles()</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns the list of targets set up by the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="b-Install"><function>Install</function></link>
or
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="b-InstallAs"><function>InstallAs</function></link>
builders.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
This function serves as a convenient method to select the contents of
a binary package.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Install( '/bin', [ 'executable_a', 'executable_b' ] )

# will return the file node list
# [ '/bin/executable_a', '/bin/executable_b' ]
FindInstalledFiles()

Install( '/lib', [ 'some_library' ] )

# will return the file node list
# [ '/bin/executable_a', '/bin/executable_b', '/lib/some_library' ]
FindInstalledFiles()
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-FindPathDirs">
    <term>
      <literal>FindPathDirs(variable)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns a function
(actually a callable Python object)
intended to be used as the
<varname>path_function</varname>
of a Scanner object.
The returned object will look up the specified
<varname>variable</varname>
in a construction environment
and treat the construction variable's value as a list of
directory paths that should be searched
(like
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="cv-CPPPATH"><envar>$CPPPATH</envar></link>,
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="cv-LIBPATH"><envar>$LIBPATH</envar></link>,
etc.).
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that use of
<function xmlns="http://www.scons.org/dbxsd/v1.0">FindPathDirs</function>
is generally preferable to
writing your own
<varname>path_function</varname>
for the following reasons:
1) The returned list will contain all appropriate directories
found in source trees
(when
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-VariantDir"><function>VariantDir</function></link>
is used)
or in code repositories
(when
<function xmlns="http://www.scons.org/dbxsd/v1.0">Repository</function>
or the
<option>-Y</option>
option are used).
2) scons will identify expansions of
<varname>variable</varname>
that evaluate to the same list of directories as,
in fact, the same list,
and avoid re-scanning the directories for files,
when possible.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
def my_scan(node, env, path, arg):
    # Code to scan file contents goes here...
    return include_files

scanner = Scanner(name = 'myscanner',
                  function = my_scan,
                  path_function = FindPathDirs('MYPATH'))
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-FindSourceFiles">
    <term>
      <literal>FindSourceFiles(node='"."')</literal>
    </term>
    <term>
      <literal>env.FindSourceFiles(node='"."')</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns the list of nodes which serve as the source of the built files.
It does so by inspecting the dependency tree starting at the optional
argument
<varname>node</varname>
which defaults to the '"."'-node. It will then return all leaves of
<varname>node</varname>.
These are all children which have no further children.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
This function is a convenient method to select the contents of a Source
Package.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Program( 'src/main_a.c' )
Program( 'src/main_b.c' )
Program( 'main_c.c' )

# returns ['main_c.c', 'src/main_a.c', 'SConstruct', 'src/main_b.c']
FindSourceFiles()

# returns ['src/main_b.c', 'src/main_a.c' ]
FindSourceFiles( 'src' )
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
As you can see build support files (SConstruct in the above example)
will also be returned by this function.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Flatten">
    <term>
      <literal>Flatten(sequence)</literal>
    </term>
    <term>
      <literal>env.Flatten(sequence)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Takes a sequence (that is, a Python list or tuple)
that may contain nested sequences
and returns a flattened list containing
all of the individual elements in any sequence.
This can be helpful for collecting
the lists returned by calls to Builders;
other Builders will automatically
flatten lists specified as input,
but direct Python manipulation of
these lists does not.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
foo = Object('foo.c')
bar = Object('bar.c')

# Because `foo' and `bar' are lists returned by the Object() Builder,
# `objects' will be a list containing nested lists:
objects = ['f1.o', foo, 'f2.o', bar, 'f3.o']

# Passing such a list to another Builder is all right because
# the Builder will flatten the list automatically:
Program(source = objects)

# If you need to manipulate the list directly using Python, you need to
# call Flatten() yourself, or otherwise handle nested lists:
for object in Flatten(objects):
    print str(object)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-GetBuildFailures">
    <term>
      <literal>GetBuildFailures()</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns a list of exceptions for the
actions that failed while
attempting to build targets.
Each element in the returned list is a
<classname>BuildError</classname>
object
with the following attributes
that record various aspects
of the build failure:
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>.node</literal>
The node that was being built
when the build failure occurred.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>.status</literal>
The numeric exit status
returned by the command or Python function
that failed when trying to build the
specified Node.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>.errstr</literal>
The SCons error string
describing the build failure.
(This is often a generic
message like "Error 2"
to indicate that an executed
command exited with a status of 2.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>.filename</literal>
The name of the file or
directory that actually caused the failure.
This may be different from the
<literal>.node</literal>
attribute.
For example,
if an attempt to build a target named
<filename>sub/dir/target</filename>
fails because the
<filename>sub/dir</filename>
directory could not be created,
then the
<literal>.node</literal>
attribute will be
<filename>sub/dir/target</filename>
but the
<literal>.filename</literal>
attribute will be
<filename>sub/dir</filename>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>.executor</literal>
The SCons Executor object
for the target Node
being built.
This can be used to retrieve
the construction environment used
for the failed action.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>.action</literal>
The actual SCons Action object that failed.
This will be one specific action
out of the possible list of
actions that would have been
executed to build the target.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>.command</literal>
The actual expanded command that was executed and failed,
after expansion of
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="cv-TARGET"><envar>$TARGET</envar></link>,
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="cv-SOURCE"><envar>$SOURCE</envar></link>,
and other construction variables.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that the
<function xmlns="http://www.scons.org/dbxsd/v1.0">GetBuildFailures</function>
function
will always return an empty list
until any build failure has occurred,
which means that
<function xmlns="http://www.scons.org/dbxsd/v1.0">GetBuildFailures</function>
will always return an empty list
while the
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
files are being read.
Its primary intended use is
for functions that will be
executed before SCons exits
by passing them to the
standard Python
<function>atexit.register</function>()
function.
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
import atexit

def print_build_failures():
    from SCons.Script import GetBuildFailures
    for bf in GetBuildFailures():
        print("%s failed: %s" % (bf.node, bf.errstr))

atexit.register(print_build_failures)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-GetBuildPath">
    <term>
      <literal>GetBuildPath(file, [...])</literal>
    </term>
    <term>
      <literal>env.GetBuildPath(file, [...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns the
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
path name (or names) for the specified
<varname>file</varname>
(or files).
The specified
<varname>file</varname>
or files
may be
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
Nodes or strings representing path names.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-GetLaunchDir">
    <term>
      <literal>GetLaunchDir()</literal>
    </term>
    <term>
      <literal>env.GetLaunchDir()</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns the absolute path name of the directory from which
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
was initially invoked.
This can be useful when using the
<option>-u</option>,
<option>-U</option>
or
<option>-D</option>
options, which internally
change to the directory in which the
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConstruct</filename>
file is found.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-GetOption">
    <term>
      <literal>GetOption(name)</literal>
    </term>
    <term>
      <literal>env.GetOption(name)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This function provides a way to query the value of
SCons options set on scons command line
(or set using the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-SetOption"><function>SetOption</function></link>
function).
The options supported are:
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<variablelist>
<varlistentry>
<term><literal>cache_debug</literal></term>
<listitem>
<para>
which corresponds to --cache-debug;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>cache_disable</literal></term>
<listitem>
<para>
which corresponds to --cache-disable;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>cache_force</literal></term>
<listitem>
<para>
which corresponds to --cache-force;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>cache_show</literal></term>
<listitem>
<para>
which corresponds to --cache-show;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>clean</literal></term>
<listitem>
<para>
which corresponds to -c, --clean and --remove;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>config</literal></term>
<listitem>
<para>
which corresponds to --config;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>directory</literal></term>
<listitem>
<para>
which corresponds to -C and --directory;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>diskcheck</literal></term>
<listitem>
<para>
which corresponds to --diskcheck
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>duplicate</literal></term>
<listitem>
<para>
which corresponds to --duplicate;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>file</literal></term>
<listitem>
<para>
which corresponds to -f, --file, --makefile and --sconstruct;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>help</literal></term>
<listitem>
<para>
which corresponds to -h and --help;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ignore_errors</literal></term>
<listitem>
<para>
which corresponds to --ignore-errors;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>implicit_cache</literal></term>
<listitem>
<para>
which corresponds to --implicit-cache;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>implicit_deps_changed</literal></term>
<listitem>
<para>
which corresponds to --implicit-deps-changed;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>implicit_deps_unchanged</literal></term>
<listitem>
<para>
which corresponds to --implicit-deps-unchanged;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>interactive</literal></term>
<listitem>
<para>
which corresponds to --interact and --interactive;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>keep_going</literal></term>
<listitem>
<para>
which corresponds to -k and --keep-going;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>max_drift</literal></term>
<listitem>
<para>
which corresponds to --max-drift;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>no_exec</literal></term>
<listitem>
<para>
which corresponds to -n, --no-exec, --just-print, --dry-run and --recon;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>no_site_dir</literal></term>
<listitem>
<para>
which corresponds to --no-site-dir;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>num_jobs</literal></term>
<listitem>
<para>
which corresponds to -j and --jobs;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>profile_file</literal></term>
<listitem>
<para>
which corresponds to --profile;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>question</literal></term>
<listitem>
<para>
which corresponds to -q and --question;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>random</literal></term>
<listitem>
<para>
which corresponds to --random;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>repository</literal></term>
<listitem>
<para>
which corresponds to -Y, --repository and --srcdir;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>silent</literal></term>
<listitem>
<para>
which corresponds to -s, --silent and --quiet;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>site_dir</literal></term>
<listitem>
<para>
which corresponds to --site-dir;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>stack_size</literal></term>
<listitem>
<para>
which corresponds to --stack-size;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>taskmastertrace_file</literal></term>
<listitem>
<para>
which corresponds to --taskmastertrace; and
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>warn</literal></term>
<listitem>
<para>
which corresponds to --warn and --warning.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
See the documentation for the
corresponding command line object for information about each specific
option.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Glob">
    <term>
      <literal>Glob(pattern, [ondisk, source, strings, exclude])</literal>
    </term>
    <term>
      <literal>env.Glob(pattern, [ondisk, source, strings, exclude])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns Nodes (or strings) that match the specified
<varname>pattern</varname>,
relative to the directory of the current
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
file.
The
<function>env.Glob</function>()
form performs string substition on
<varname>pattern</varname>
and returns whatever matches
the resulting expanded pattern.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The specified
<varname>pattern</varname>
uses Unix shell style metacharacters for matching:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
  *       matches everything
  ?       matches any single character
  [seq]   matches any character in seq
  [!seq]  matches any char not in seq
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the first character of a filename is a dot,
it must be matched explicitly.
Character matches do
<emphasis>not</emphasis>
span directory separators.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">Glob</function>
knows about
repositories
(see the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Repository"><function>Repository</function></link>
function)
and source directories
(see the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-VariantDir"><function>VariantDir</function></link>
function)
and
returns a Node (or string, if so configured)
in the local (SConscript) directory
if matching Node is found
anywhere in a corresponding
repository or source directory.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<varname>ondisk</varname>
argument may be set to
<literal>False</literal>
(or any other non-true value)
to disable the search for matches on disk,
thereby only returning matches among
already-configured File or Dir Nodes.
The default behavior is to
return corresponding Nodes
for any on-disk matches found.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<varname>source</varname>
argument may be set to
<literal>True</literal>
(or any equivalent value)
to specify that,
when the local directory is a
<function xmlns="http://www.scons.org/dbxsd/v1.0">VariantDir</function>,
the returned Nodes should be from the
corresponding source directory,
not the local directory.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<varname>strings</varname>
argument may be set to
<literal>True</literal>
(or any equivalent value)
to have the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Glob</function>
function return strings, not Nodes,
that represent the matched files or directories.
The returned strings will be relative to
the local (SConscript) directory.
(Note that This may make it easier to perform
arbitrary manipulation of file names,
but if the returned strings are
passed to a different
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
file,
any Node translation will be relative
to the other
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
directory,
not the original
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
directory.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<varname>exclude</varname>
argument may be set to a pattern or a list of patterns
(following the same Unix shell semantics)
which must be filtered out of returned elements.
Elements matching a least one pattern of
this list will be excluded.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Program('foo', Glob('*.c'))
Zip('/tmp/everything', Glob('.??*') + Glob('*'))
sources = Glob('*.cpp', exclude=['os_*_specific_*.cpp']) + Glob('os_%s_specific_*.cpp'%currentOS)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Help">
    <term>
      <literal>Help(text, append=False)</literal>
    </term>
    <term>
      <literal>env.Help(text, append=False)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This specifies help text to be printed if the
<option>-h</option>
argument is given to
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>.
If 
<function xmlns="http://www.scons.org/dbxsd/v1.0">Help</function>
is called multiple times, the text is appended together in the order that 
<function xmlns="http://www.scons.org/dbxsd/v1.0">Help</function>
is called. With append set to False, any 
<function xmlns="http://www.scons.org/dbxsd/v1.0">Help</function>
text generated with 
<function xmlns="http://www.scons.org/dbxsd/v1.0">AddOption</function>
is clobbered. If append is True, the AddOption help is prepended to the help
string, thus preserving the 
<option>-h</option>
message.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Ignore">
    <term>
      <literal>Ignore(target, dependency)</literal>
    </term>
    <term>
      <literal>env.Ignore(target, dependency)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
The specified dependency file(s)
will be ignored when deciding if
the target file(s) need to be rebuilt.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
You can also use
<function xmlns="http://www.scons.org/dbxsd/v1.0">Ignore</function>
to remove a target from the default build.
In order to do this you must specify the directory the target will
be built in as the target, and the file you want to skip building
as the dependency.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that this will only remove the dependencies listed from
the files built by default.  It will still be built if that
dependency is needed by another object being built.
See the third and forth examples below.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Ignore('foo', 'foo.c')
env.Ignore('bar', ['bar1.h', 'bar2.h'])
env.Ignore('.','foobar.obj')
env.Ignore('bar','bar/foobar.obj')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Import">
    <term>
      <literal>Import(vars)</literal>
    </term>
    <term>
      <literal>env.Import(vars)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This tells
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to import a list of variables into the current SConscript file. This
will import variables that were exported with
<function xmlns="http://www.scons.org/dbxsd/v1.0">Export</function>
or in the
<varname>exports</varname>
argument to
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-SConscript"><function>SConscript</function></link>.
Variables exported by
<function xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</function>
have precedence.
Multiple variable names can be passed to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Import</function>
as separate arguments or as a list. The variable "*" can be used
to import all variables.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Import("env")
Import("env", "variable")
Import(["env", "variable"])
Import("*")
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Literal">
    <term>
      <literal>Literal(string)</literal>
    </term>
    <term>
      <literal>env.Literal(string)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
The specified
<varname>string</varname>
will be preserved as-is
and not have construction variables expanded.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Local">
    <term>
      <literal>Local(targets)</literal>
    </term>
    <term>
      <literal>env.Local(targets)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
The specified
<varname>targets</varname>
will have copies made in the local tree,
even if an already up-to-date copy
exists in a repository.
Returns a list of the target Node or Nodes.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-MergeFlags">
    <term>
      <literal>env.MergeFlags(arg, [unique])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Merges the specified
<varname>arg</varname>
values to the construction environment's construction variables.
If the
<varname>arg</varname>
argument is not a dictionary,
it is converted to one by calling
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-ParseFlags"><function>env.ParseFlags</function></link>
on the argument
before the values are merged.
Note that
<varname>arg</varname>
must be a single value,
so multiple strings must
be passed in as a list,
not as separate arguments to
<function xmlns="http://www.scons.org/dbxsd/v1.0">env.MergeFlags</function>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
By default,
duplicate values are eliminated;
you can, however, specify
<literal>unique=0</literal>
to allow duplicate
values to be added.
When eliminating duplicate values,
any construction variables that end with
the string
<literal>PATH</literal>
keep the left-most unique value.
All other construction variables keep
the right-most unique value.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# Add an optimization flag to $CCFLAGS.
env.MergeFlags('-O3')

# Combine the flags returned from running pkg-config with an optimization
# flag and merge the result into the construction variables.
env.MergeFlags(['!pkg-config gtk+-2.0 --cflags', '-O3'])

# Combine an optimization flag with the flags returned from running pkg-config
# twice and merge the result into the construction variables.
env.MergeFlags(['-O3',
               '!pkg-config gtk+-2.0 --cflags --libs',
               '!pkg-config libpng12 --cflags --libs'])
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-NoCache">
    <term>
      <literal>NoCache(target, ...)</literal>
    </term>
    <term>
      <literal>env.NoCache(target, ...)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies a list of files which should
<emphasis>not</emphasis>
be cached whenever the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-CacheDir"><function>CacheDir</function></link>
method has been activated.
The specified targets may be a list
or an individual target.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Multiple files should be specified
either as separate arguments to the
<function xmlns="http://www.scons.org/dbxsd/v1.0">NoCache</function>
method, or as a list.
<function xmlns="http://www.scons.org/dbxsd/v1.0">NoCache</function>
will also accept the return value of any of the construction environment
Builder methods.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Calling
<function xmlns="http://www.scons.org/dbxsd/v1.0">NoCache</function>
on directories and other non-File Node types has no effect because
only File Nodes are cached.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
NoCache('foo.elf')
NoCache(env.Program('hello', 'hello.c'))
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-NoClean">
    <term>
      <literal>NoClean(target, ...)</literal>
    </term>
    <term>
      <literal>env.NoClean(target, ...)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies a list of files or directories which should
<emphasis>not</emphasis>
be removed whenever the targets (or their dependencies)
are specified with the
<option>-c</option>
command line option.
The specified targets may be a list
or an individual target.
Multiple calls to
<function xmlns="http://www.scons.org/dbxsd/v1.0">NoClean</function>
are legal,
and prevent each specified target
from being removed by calls to the
<option>-c</option>
option.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Multiple files or directories should be specified
either as separate arguments to the
<function xmlns="http://www.scons.org/dbxsd/v1.0">NoClean</function>
method, or as a list.
<function xmlns="http://www.scons.org/dbxsd/v1.0">NoClean</function>
will also accept the return value of any of the construction environment
Builder methods.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Calling
<function xmlns="http://www.scons.org/dbxsd/v1.0">NoClean</function>
for a target overrides calling
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Clean"><function>Clean</function></link>
for the same target,
and any targets passed to both functions will
<emphasis>not</emphasis>
be removed by the
<option>-c</option>
option.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
NoClean('foo.elf')
NoClean(env.Program('hello', 'hello.c'))
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-ParseConfig">
    <term>
      <literal>env.ParseConfig(command, [function, unique])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Calls the specified
<varname>function</varname>
to modify the environment as specified by the output of
<varname>command</varname>.
The default
<varname>function</varname>
is
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-MergeFlags"><function>env.MergeFlags</function></link>,
which expects the output of a typical
<application>*-config</application>
command
(for example,
<application>gtk-config</application>)
and adds the options
to the appropriate construction variables.
By default,
duplicate values are not
added to any construction variables;
you can specify
<literal>unique=0</literal>
to allow duplicate
values to be added.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Interpreted options
and the construction variables they affect
are as specified for the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-ParseFlags"><function>env.ParseFlags</function></link>
method (which this method calls).
See that method's description, below,
for a table of options and construction variables.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-ParseDepends">
    <term>
      <literal>ParseDepends(filename, [must_exist, only_one])</literal>
    </term>
    <term>
      <literal>env.ParseDepends(filename, [must_exist, only_one])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Parses the contents of the specified
<varname>filename</varname>
as a list of dependencies in the style of
<application xmlns="http://www.scons.org/dbxsd/v1.0">Make</application>
or
<application>mkdep</application>,
and explicitly establishes all of the listed dependencies.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
By default,
it is not an error
if the specified
<varname>filename</varname>
does not exist.
The optional
<varname>must_exist</varname>
argument may be set to a non-zero
value to have
scons
throw an exception and
generate an error if the file does not exist,
or is otherwise inaccessible.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The optional
<varname>only_one</varname>
argument may be set to a non-zero
value to have
scons
thrown an exception and
generate an error
if the file contains dependency
information for more than one target.
This can provide a small sanity check
for files intended to be generated
by, for example, the
<literal>gcc -M</literal>
flag,
which should typically only
write dependency information for
one output file into a corresponding
<filename>.d</filename>
file.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<varname>filename</varname>
and all of the files listed therein
will be interpreted relative to
the directory of the
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
file which calls the
<function xmlns="http://www.scons.org/dbxsd/v1.0">ParseDepends</function>
function.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-ParseFlags">
    <term>
      <literal>env.ParseFlags(flags, ...)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Parses one or more strings containing
typical command-line flags for GCC tool chains
and returns a dictionary with the flag values
separated into the appropriate SCons construction variables.
This is intended as a companion to the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-MergeFlags"><function>env.MergeFlags</function></link>
method, but allows for the values in the returned dictionary
to be modified, if necessary,
before merging them into the construction environment.
(Note that
<function xmlns="http://www.scons.org/dbxsd/v1.0">env.MergeFlags</function>
will call this method if its argument is not a dictionary,
so it is usually not necessary to call
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-ParseFlags"><function>env.ParseFlags</function></link>
directly unless you want to manipulate the values.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the first character in any string is
an exclamation mark (!),
the rest of the string is executed as a command,
and the output from the command is
parsed as GCC tool chain command-line flags
and added to the resulting dictionary.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Flag values are translated accordig to the prefix found,
and added to the following construction variables:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
-arch               CCFLAGS, LINKFLAGS
-D                  CPPDEFINES
-framework          FRAMEWORKS
-frameworkdir=      FRAMEWORKPATH
-include            CCFLAGS
-isysroot           CCFLAGS, LINKFLAGS
-isystem            CCFLAGS
-iquote             CCFLAGS
-idirafter          CCFLAGS
-I                  CPPPATH
-l                  LIBS
-L                  LIBPATH
-mno-cygwin         CCFLAGS, LINKFLAGS
-mwindows           LINKFLAGS
-pthread            CCFLAGS, LINKFLAGS
-std=               CFLAGS
-Wa,                ASFLAGS, CCFLAGS
-Wl,-rpath=         RPATH
-Wl,-R,             RPATH
-Wl,-R              RPATH
-Wl,                LINKFLAGS
-Wp,                CPPFLAGS
-                   CCFLAGS
+                   CCFLAGS, LINKFLAGS
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Any other strings not associated with options
are assumed to be the names of libraries
and added to the
<envar xmlns="http://www.scons.org/dbxsd/v1.0">$LIBS</envar>
construction variable.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples (all of which produce the same result):
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
dict = env.ParseFlags('-O2 -Dfoo -Dbar=1')
dict = env.ParseFlags('-O2', '-Dfoo', '-Dbar=1')
dict = env.ParseFlags(['-O2', '-Dfoo -Dbar=1'])
dict = env.ParseFlags('-O2', '!echo -Dfoo -Dbar=1')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Platform">
    <term>
      <literal>Platform(string)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">Platform</function>
form returns a callable object
that can be used to initialize
a construction environment using the
platform keyword of the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Environment</function>
function.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env = Environment(platform = Platform('win32'))
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">env.Platform</function>
form applies the callable object for the specified platform
<varname>string</varname>
to the environment through which the method was called.
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Platform('posix')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that the
<literal>win32</literal>
platform adds the
<literal>SystemDrive</literal>
and
<literal>SystemRoot</literal>
variables from the user's external environment
to the construction environment's
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="cv-ENV"><envar>$ENV</envar></link>
dictionary.
This is so that any executed commands
that use sockets to connect with other systems
(such as fetching source files from
external CVS repository specifications like
<literal>:pserver:anonymous@cvs.sourceforge.net:/cvsroot/scons</literal>)
will work on Windows systems.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Precious">
    <term>
      <literal>Precious(target, ...)</literal>
    </term>
    <term>
      <literal>env.Precious(target, ...)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Marks each given
<varname>target</varname>
as precious so it is not deleted before it is rebuilt. Normally
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
deletes a target before building it.
Multiple targets can be passed in to a single call to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Precious</function>.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Prepend">
    <term>
      <literal>env.Prepend(key=val, [...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Appends the specified keyword arguments
to the beginning of construction variables in the environment.
If the Environment does not have
the specified construction variable,
it is simply added to the environment.
If the values of the construction variable
and the keyword argument are the same type,
then the two values will be simply added together.
Otherwise, the construction variable
and the value of the keyword argument
are both coerced to lists,
and the lists are added together.
(See also the Append method, above.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Prepend(CCFLAGS = '-g ', FOO = ['foo.yyy'])
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-PrependENVPath">
    <term>
      <literal>env.PrependENVPath(name, newpath, [envname, sep, delete_existing])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This appends new path elements to the given path in the
specified external environment
(<envar xmlns="http://www.scons.org/dbxsd/v1.0">$ENV</envar>
by default).
This will only add
any particular path once (leaving the first one it encounters and
ignoring the rest, to preserve path order),
and to help assure this,
will normalize all paths (using
<literal>os.path.normpath</literal>
and
<literal>os.path.normcase</literal>).
This can also handle the
case where the given old path variable is a list instead of a
string, in which case a list will be returned instead of a string.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<varname>delete_existing</varname>
is 0, then adding a path that already exists
will not move it to the beginning;
it will stay where it is in the list.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
print 'before:',env['ENV']['INCLUDE']
include_path = '/foo/bar:/foo'
env.PrependENVPath('INCLUDE', include_path)
print 'after:',env['ENV']['INCLUDE']
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The above example will print:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
before: /biz:/foo
after: /foo/bar:/foo:/biz
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-PrependUnique">
    <term>
      <literal>env.PrependUnique(key=val, delete_existing=0, [...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Appends the specified keyword arguments
to the beginning of construction variables in the environment.
If the Environment does not have
the specified construction variable,
it is simply added to the environment.
If the construction variable being appended to is a list,
then any value(s) that already exist in the
construction variable will
<emphasis>not</emphasis>
be added again to the list.
However, if delete_existing is 1,
existing matching values are removed first, so
existing values in the arg list move to the front of the list.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.PrependUnique(CCFLAGS = '-g', FOO = ['foo.yyy'])
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Progress">
    <term>
      <literal>Progress(callable, [interval])</literal>
    </term>
    <term>
      <literal>Progress(string, [interval, file, overwrite])</literal>
    </term>
    <term>
      <literal>Progress(list_of_strings, [interval, file, overwrite])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Allows SCons to show progress made during the build
by displaying a string or calling a function while
evaluating Nodes (e.g. files).
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the first specified argument is a Python callable
(a function or an object that has a
<function>__call__</function>()
method),
the function will be called
once every
<varname>interval</varname>
times a Node is evaluated.
The callable will be passed the evaluated Node
as its only argument.
(For future compatibility,
it's a good idea to also add
<literal>*args</literal>
and
<literal>**kw</literal>
as arguments to your function or method.
This will prevent the code from breaking
if SCons ever changes the interface
to call the function with additional arguments in the future.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
An example of a simple custom progress function
that prints a string containing the Node name
every 10 Nodes:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
def my_progress_function(node, *args, **kw):
    print('Evaluating node %s!' % node)
Progress(my_progress_function, interval=10)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
A more complicated example of a custom progress display object
that prints a string containing a count
every 100 evaluated Nodes.
Note the use of
<literal>\r</literal>
(a carriage return)
at the end so that the string
will overwrite itself on a display:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
import sys
class ProgressCounter(object):
    count = 0
    def __call__(self, node, *args, **kw):
        self.count += 100
        sys.stderr.write('Evaluated %s nodes\r' % self.count)
Progress(ProgressCounter(), interval=100)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the first argument
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Progress"><function>Progress</function></link>
is a string,
the string will be displayed
every
<varname>interval</varname>
evaluated Nodes.
The default is to print the string on standard output;
an alternate output stream
may be specified with the
<literal>file=</literal>
argument.
The following will print a series of dots
on the error output,
one dot for every 100 evaluated Nodes:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
import sys
Progress('.', interval=100, file=sys.stderr)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the string contains the verbatim substring
<envar xmlns="http://www.scons.org/dbxsd/v1.0">$TARGET</envar>,
it will be replaced with the Node.
Note that, for performance reasons, this is
<emphasis>not</emphasis>
a regular SCons variable substition,
so you can not use other variables
or use curly braces.
The following example will print the name of
every evaluated Node,
using a
<literal>\r</literal>
(carriage return) to cause each line to overwritten by the next line,
and the
<literal>overwrite=</literal>
keyword argument to make sure the previously-printed
file name is overwritten with blank spaces:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
import sys
Progress('$TARGET\r', overwrite=True)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the first argument to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Progress</function>
is a list of strings,
then each string in the list will be displayed
in rotating fashion every
<varname>interval</varname>
evaluated Nodes.
This can be used to implement a "spinner"
on the user's screen as follows:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
Progress(['-\r', '\\\r', '|\r', '/\r'], interval=5)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Pseudo">
    <term>
      <literal>Pseudo(target, ...)</literal>
    </term>
    <term>
      <literal>env.Pseudo(target, ...)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This indicates that each given
<varname>target</varname>
should not be created by the build rule, and if the target is created,
an error will be generated. This is similar to the gnu make .PHONY
target. However, in the vast majority of cases, an
<function xmlns="http://www.scons.org/dbxsd/v1.0">Alias</function>
is more appropriate.

Multiple targets can be passed in to a single call to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Pseudo</function>.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-PyPackageDir">
    <term>
      <literal>PyPackageDir(modulename)</literal>
    </term>
    <term>
      <literal>env.PyPackageDir(modulename)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This returns a Directory Node similar to Dir.
The python module / package is looked up and if located
the directory is returned for the location.
<varname>modulename</varname>
Is a named python package / module to
lookup the directory for it's location.
</para>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<varname>modulename</varname>
is a list, SCons returns a list of Dir nodes.
Construction variables are expanded in
<varname>modulename</varname>.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Replace">
    <term>
      <literal>env.Replace(key=val, [...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Replaces construction variables in the Environment
with the specified keyword arguments.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Replace(CCFLAGS = '-g', FOO = 'foo.xxx')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Repository">
    <term>
      <literal>Repository(directory)</literal>
    </term>
    <term>
      <literal>env.Repository(directory)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies that
<varname>directory</varname>
is a repository to be searched for files.
Multiple calls to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Repository</function>
are legal,
and each one adds to the list of
repositories that will be searched.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
To
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>,
a repository is a copy of the source tree,
from the top-level directory on down,
which may contain
both source files and derived files
that can be used to build targets in
the local source tree.
The canonical example would be an
official source tree maintained by an integrator.
If the repository contains derived files,
then the derived files should have been built using
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>,
so that the repository contains the necessary
signature information to allow
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to figure out when it is appropriate to
use the repository copy of a derived file,
instead of building one locally.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that if an up-to-date derived file
already exists in a repository,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will
<emphasis>not</emphasis>
make a copy in the local directory tree.
In order to guarantee that a local copy
will be made,
use the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Local"><function>Local</function></link>
method.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Requires">
    <term>
      <literal>Requires(target, prerequisite)</literal>
    </term>
    <term>
      <literal>env.Requires(target, prerequisite)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Specifies an order-only relationship
between the specified target file(s)
and the specified prerequisite file(s).
The prerequisite file(s)
will be (re)built, if necessary,
<emphasis>before</emphasis>
the target file(s),
but the target file(s) do not actually
depend on the prerequisites
and will not be rebuilt simply because
the prerequisite file(s) change.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Requires('foo', 'file-that-must-be-built-before-foo')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Return">
    <term>
      <literal>Return([vars..., stop=])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
By default,
this stops processing the current SConscript
file and returns to the calling SConscript file
the values of the variables named in the
<varname>vars</varname>
string arguments.
Multiple strings contaning variable names may be passed to
<function xmlns="http://www.scons.org/dbxsd/v1.0">Return</function>.
Any strings that contain white space
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The optional
<literal>stop=</literal>
keyword argument may be set to a false value
to continue processing the rest of the SConscript
file after the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Return</function>
call.
This was the default behavior prior to SCons 0.98.
However, the values returned
are still the values of the variables in the named
<varname>vars</varname>
at the point
<function xmlns="http://www.scons.org/dbxsd/v1.0">Return</function>
is called.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# Returns without returning a value.
Return()

# Returns the value of the 'foo' Python variable.
Return("foo")

# Returns the values of the Python variables 'foo' and 'bar'.
Return("foo", "bar")

# Returns the values of Python variables 'val1' and 'val2'.
Return('val1 val2')
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Scanner">
    <term>
      <literal>Scanner(function, [argument, keys, path_function, node_class, node_factory, scan_check, recursive])</literal>
    </term>
    <term>
      <literal>env.Scanner(function, [argument, keys, path_function, node_class, node_factory, scan_check, recursive])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Creates a Scanner object for
the specified
<varname>function</varname>.
See the section "Scanner Objects,"
below, for a complete explanation of the arguments and behavior.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-SConscript">
    <term>
      <literal>SConscript(scripts, [exports, variant_dir, duplicate, must_exist])</literal>
    </term>
    <term>
      <literal>env.SConscript(scripts, [exports, variant_dir, duplicate, must_exist])</literal>
    </term>
    <term>
      <literal>SConscript(dirs=subdirs, [name=script, exports, variant_dir, duplicate, must_exist])</literal>
    </term>
    <term>
      <literal>env.SConscript(dirs=subdirs, [name=script, exports, variant_dir, duplicate, must_exist])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This tells
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to execute
one or more subsidiary SConscript (configuration) files.
Any variables returned by a called script using
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Return"><function>Return</function></link>
will be returned by the call to
<function xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</function>.
There are two ways to call the
<function xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</function>
function.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The first way you can call
<function xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</function>
is to explicitly specify one or more
<varname>scripts</varname>
as the first argument.
A single script may be specified as a string;
multiple scripts must be specified as a list
(either explicitly or as created by
a function like
<function xmlns="http://www.scons.org/dbxsd/v1.0">Split</function>).
Examples:
</para>
<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
SConscript('SConscript')      # run SConscript in the current directory
SConscript('src/SConscript')  # run SConscript in the src directory
SConscript(['src/SConscript', 'doc/SConscript'])
config = SConscript('MyConfig.py')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The second way you can call
<function xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</function>
is to specify a list of (sub)directory names
as a
<literal>dirs=</literal><varname>subdirs</varname>
keyword argument.
In this case,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will, by default,
execute a subsidiary configuration file named
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
in each of the specified directories.
You may specify a name other than
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
by supplying an optional
<literal>name=</literal><varname>script</varname>
keyword argument.
The first three examples below have the same effect
as the first three examples above:
</para>
<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
SConscript(dirs='.')      # run SConscript in the current directory
SConscript(dirs='src')    # run SConscript in the src directory
SConscript(dirs=['src', 'doc'])
SConscript(dirs=['sub1', 'sub2'], name='MySConscript')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The optional
<varname>exports</varname>
argument provides a list of variable names or a dictionary of
named values to export to the
<varname>script(s)</varname>.
These variables are locally exported only to the specified
<varname>script(s)</varname>,
and do not affect the global pool of variables used by the
<function xmlns="http://www.scons.org/dbxsd/v1.0">Export</function>
function.
<!-- If multiple dirs are provided, each script gets a fresh export. -->
The subsidiary
<varname>script(s)</varname>
must use the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Import"><function>Import</function></link>
function to import the variables.
Examples:
</para>
<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
foo = SConscript('sub/SConscript', exports='env')
SConscript('dir/SConscript', exports=['env', 'variable'])
SConscript(dirs='subdir', exports='env variable')
SConscript(dirs=['one', 'two', 'three'], exports='shared_info')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the optional
<varname>variant_dir</varname>
argument is present, it causes an effect equivalent to the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-VariantDir"><function>VariantDir</function></link>
method described below.
(If
<varname>variant_dir</varname>
is not present, the
<!-- <varname>src_dir</varname> and -->
<varname>duplicate</varname>
<!-- arguments are ignored.) -->
argument is ignored.)
The
<varname>variant_dir</varname>
<!--
and
<varname>src_dir</varname>
arguments are interpreted relative to the directory of the calling
-->
argument is interpreted relative to the directory of the calling
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
file.
See the description of the
<function xmlns="http://www.scons.org/dbxsd/v1.0">VariantDir</function>
function below for additional details and restrictions.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<varname>variant_dir</varname>
is present,
<!--
but
<varname>src_dir</varname>
is not,
-->
the source directory is the directory in which the
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
file resides and the
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename>
file is evaluated as if it were in the
<varname>variant_dir</varname>
directory:
</para>
<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
SConscript('src/SConscript', variant_dir = 'build')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
is equivalent to
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
VariantDir('build', 'src')
SConscript('build/SConscript')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
This later paradigm is often used when the sources are
in the same directory as the
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConstruct</filename>:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
SConscript('SConscript', variant_dir = 'build')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
is equivalent to
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
VariantDir('build', '.')
SConscript('build/SConscript')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<!--
If
<varname>variant_dir</varname>
and"
<varname>src_dir</varname>
are both present,
xxxxx everything is in a state of confusion.
</para>
<example_commands>
SConscript(dirs = 'src', variant_dir = 'build', src_dir = '.')
runs src/SConscript in build/src, but
SConscript(dirs = 'lib', variant_dir = 'build', src_dir = 'src')
runs lib/SConscript (in lib!).  However,
SConscript(dirs = 'src', variant_dir = 'build', src_dir = 'src')
runs src/SConscript in build.  Moreover,
SConscript(dirs = 'src/lib', variant_dir = 'build', src_dir = 'src')
runs src/lib/SConscript in build/lib.  Moreover,
SConscript(dirs = 'build/src/lib', variant_dir = 'build', src_dir = 'src')
can't find build/src/lib/SConscript, even though it ought to exist.
</example_commands>
<para>
is equivalent to
</para>
<example_commands>
????????????????
</example_commands>
<para>
and what about this alternative?
TODO??? SConscript('build/SConscript', src_dir='src')
-->
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The optional
<varname>must_exist</varname>
argument, if true, causes an exception to be raised if a requested
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConscript</filename> file is not found. The current default is false,
causing only a warning to be omitted, but this behavior is deprecated.
For scripts which truly intend to be optional, transition to
explicty supplying
<literal>must_exist=False</literal> to the call.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Here are some composite examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# collect the configuration information and use it to build src and doc
shared_info = SConscript('MyConfig.py')
SConscript('src/SConscript', exports='shared_info')
SConscript('doc/SConscript', exports='shared_info')
</example_commands>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# build debugging and production versions.  SConscript
# can use Dir('.').path to determine variant.
SConscript('SConscript', variant_dir='debug', duplicate=0)
SConscript('SConscript', variant_dir='prod', duplicate=0)
</example_commands>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# build debugging and production versions.  SConscript
# is passed flags to use.
opts = { 'CPPDEFINES' : ['DEBUG'], 'CCFLAGS' : '-pgdb' }
SConscript('SConscript', variant_dir='debug', duplicate=0, exports=opts)
opts = { 'CPPDEFINES' : ['NODEBUG'], 'CCFLAGS' : '-O' }
SConscript('SConscript', variant_dir='prod', duplicate=0, exports=opts)
</example_commands>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# build common documentation and compile for different architectures
SConscript('doc/SConscript', variant_dir='build/doc', duplicate=0)
SConscript('src/SConscript', variant_dir='build/x86', duplicate=0)
SConscript('src/SConscript', variant_dir='build/ppc', duplicate=0)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-SConscriptChdir">
    <term>
      <literal>SConscriptChdir(value)</literal>
    </term>
    <term>
      <literal>env.SConscriptChdir(value)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
By default,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
changes its working directory
to the directory in which each
subsidiary SConscript file lives.
This behavior may be disabled
by specifying either:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
SConscriptChdir(0)
env.SConscriptChdir(0)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
in which case
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will stay in the top-level directory
while reading all SConscript files.
(This may be necessary when building from repositories,
when all the directories in which SConscript files may be found
don't necessarily exist locally.)
You may enable and disable
this ability by calling
SConscriptChdir()
multiple times.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env = Environment()
SConscriptChdir(0)
SConscript('foo/SConscript')	# will not chdir to foo
env.SConscriptChdir(1)
SConscript('bar/SConscript')	# will chdir to bar
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-SConsignFile">
    <term>
      <literal>SConsignFile([file, dbm_module])</literal>
    </term>
    <term>
      <literal>env.SConsignFile([file, dbm_module])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This tells
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to store all file signatures
in the specified database
<varname>file</varname>.
If the
<varname>file</varname>
name is omitted,
<filename>.sconsign</filename>
is used by default.
(The actual file name(s) stored on disk
may have an appropriated suffix appended
by the
<varname> dbm_module</varname>.)
If
<varname>file</varname>
is not an absolute path name,
the file is placed in the same directory as the top-level
<filename xmlns="http://www.scons.org/dbxsd/v1.0">SConstruct</filename>
file.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If
<varname>file</varname>
is
<literal>None</literal>,
then
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will store file signatures
in a separate
<filename>.sconsign</filename>
file in each directory,
not in one global database file.
(This was the default behavior
prior to SCons 0.96.91 and 0.97.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The optional
<varname>dbm_module</varname>
argument can be used to specify
which Python database module
The default is to use a custom
<filename>SCons.dblite</filename>
module that uses pickled
Python data structures,
and which works on all Python versions.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# Explicitly stores signatures in ".sconsign.dblite"
# in the top-level SConstruct directory (the
# default behavior).
SConsignFile()

# Stores signatures in the file "etc/scons-signatures"
# relative to the top-level SConstruct directory.
SConsignFile("etc/scons-signatures")

# Stores signatures in the specified absolute file name.
SConsignFile("/home/me/SCons/signatures")

# Stores signatures in a separate .sconsign file
# in each directory.
SConsignFile(None)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-SetDefault">
    <term>
      <literal>env.SetDefault(key=val, [...])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Sets construction variables to default values specified with the keyword
arguments if (and only if) the variables are not already set.
The following statements are equivalent:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.SetDefault(FOO = 'foo')

if 'FOO' not in env: env['FOO'] = 'foo'
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-SetOption">
    <term>
      <literal>SetOption(name, value)</literal>
    </term>
    <term>
      <literal>env.SetOption(name, value)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This function provides a way to set a select subset of the scons command
line options from a SConscript file. The options supported are:
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<variablelist>
<varlistentry>
<term><literal>clean</literal></term>
<listitem>
<para>
which corresponds to -c, --clean and --remove;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>duplicate</literal></term>
<listitem>
<para>
which corresponds to --duplicate;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>help</literal></term>
<listitem>
<para>
which corresponds to -h and --help;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>implicit_cache</literal></term>
<listitem>
<para>
which corresponds to --implicit-cache;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>max_drift</literal></term>
<listitem>
<para>
which corresponds to --max-drift;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>no_exec</literal></term>
<listitem>
<para>
which corresponds to -n, --no-exec, --just-print, --dry-run and --recon;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>num_jobs</literal></term>
<listitem>
<para>
which corresponds to -j and --jobs;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>random</literal></term>
<listitem>
<para>
which corresponds to --random; and
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>silent</literal></term>
<listitem>
<para>
which corresponds to --silent.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>stack_size</literal></term>
<listitem>
<para>
which corresponds to --stack-size.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
See the documentation for the
corresponding command line object for information about each specific
option.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
SetOption('max_drift', 1)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-SideEffect">
    <term>
      <literal>SideEffect(side_effect, target)</literal>
    </term>
    <term>
      <literal>env.SideEffect(side_effect, target)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Declares
<varname>side_effect</varname>
as a side effect of building
<varname>target</varname>.
Both
<varname>side_effect</varname>
and
<varname>target</varname>
can be a list, a file name, or a node.
A side effect is a target file that is created or updated
as a side effect of building other targets.
For example, a Windows PDB
file is created as a side effect of building the .obj
files for a static library,
and various log files are created updated
as side effects of various TeX commands.
If a target is a side effect of multiple build commands,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will ensure that only one set of commands
is executed at a time.
Consequently, you only need to use this method
for side-effect targets that are built as a result of
multiple build commands.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Because multiple build commands may update
the same side effect file,
by default the
<varname>side_effect</varname>
target is
<emphasis>not</emphasis>
automatically removed
when the
<varname>target</varname>
is removed by the
<option>-c</option>
option.
(Note, however, that the
<varname>side_effect</varname>
might be removed as part of
cleaning the directory in which it lives.)
If you want to make sure the
<varname>side_effect</varname>
is cleaned whenever a specific
<varname>target</varname>
is cleaned,
you must specify this explicitly
with the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Clean"><function>Clean</function></link>
or
<function xmlns="http://www.scons.org/dbxsd/v1.0">env.Clean</function>
function.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-SourceCode">
    <term>
      <literal>SourceCode(entries, builder)</literal>
    </term>
    <term>
      <literal>env.SourceCode(entries, builder)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
This function and its associate factory functions are deprecated.
There is no replacement.
The intended use was to keep a local tree in sync with an archive,
but in actuality the function only causes the archive
to be fetched on the first run.
Synchronizing with the archive is best done external to <application xmlns="http://www.scons.org/dbxsd/v1.0">SCons</application>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Arrange for non-existent source files to
be fetched from a source code management system
using the specified
<varname>builder</varname>.
The specified
<varname>entries</varname>
may be a Node, string or list of both,
and may represent either individual
source files or directories in which
source files can be found.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
For any non-existent source files,
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will search up the directory tree
and use the first
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceCode</function>
builder it finds.
The specified
<varname>builder</varname>
may be
<literal>None</literal>,
in which case
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will not use a builder to fetch
source files for the specified
<varname>entries</varname>,
even if a
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceCode</function>
builder has been specified
for a directory higher up the tree.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will, by default,
fetch files from SCCS or RCS subdirectories
without explicit configuration.
This takes some extra processing time
to search for the necessary
source code management files on disk.
You can avoid these extra searches
and speed up your build a little
by disabling these searches as follows:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.SourceCode('.', None)
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that if the specified
<varname>builder</varname>
is one you create by hand,
it must have an associated
construction environment to use
when fetching a source file.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
provides a set of canned factory
functions that return appropriate
Builders for various popular
source code management systems.
Canonical examples of invocation include:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.SourceCode('.', env.BitKeeper('/usr/local/BKsources'))
env.SourceCode('src', env.CVS('/usr/local/CVSROOT'))
env.SourceCode('/', env.RCS())
env.SourceCode(['f1.c', 'f2.c'], env.SCCS())
env.SourceCode('no_source.c', None)
</example_commands>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
<!-- env.SourceCode('.', env.Subversion('file:///usr/local/Subversion')) -->
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-SourceSignatures">
    <term>
      <literal>SourceSignatures(type)</literal>
    </term>
    <term>
      <literal>env.SourceSignatures(type)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note:  Although it is not yet officially deprecated,
use of this function is discouraged.
See the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Decider"><function>Decider</function></link>
function for a more flexible and straightforward way
to configure SCons' decision-making.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceSignatures</function>
function tells
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
how to decide if a source file
(a file that is not built from any other files)
has changed since the last time it
was used to build a particular target file.
Legal values are
<literal>MD5</literal>
or
<literal>timestamp</literal>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the environment method is used,
the specified type of source signature
is only used when deciding whether targets
built with that environment are up-to-date or must be rebuilt.
If the global function is used,
the specified type of source signature becomes the default
used for all decisions
about whether targets are up-to-date.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>MD5</literal>
means
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
decides that a source file has changed
if the MD5 checksum of its contents has changed since
the last time it was used to rebuild a particular target file.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>timestamp</literal>
means
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
decides that a source file has changed
if its timestamp (modification time) has changed since
the last time it was used to rebuild a particular target file.
(Note that although this is similar to the behavior of Make,
by default it will also rebuild if the dependency is
<emphasis>older</emphasis>
than the last time it was used to rebuild the target file.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
There is no different between the two behaviors
for Python
<function xmlns="http://www.scons.org/dbxsd/v1.0">Value</function>
node objects.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>MD5</literal>
signatures take longer to compute,
but are more accurate than
<literal>timestamp</literal>
signatures.
The default value is
<literal>MD5</literal>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that the default
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-TargetSignatures"><function>TargetSignatures</function></link>
setting (see below)
is to use this
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceSignatures</function>
setting for any target files that are used
to build other target files.
Consequently, changing the value of
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceSignatures</function>
will, by default,
affect the up-to-date decision for all files in the build
(or all files built with a specific construction environment
when
<function xmlns="http://www.scons.org/dbxsd/v1.0">env.SourceSignatures</function>
is used).
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Split">
    <term>
      <literal>Split(arg)</literal>
    </term>
    <term>
      <literal>env.Split(arg)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns a list of file names or other objects.
If arg is a string,
it will be split on strings of white-space characters
within the string,
making it easier to write long lists of file names.
If arg is already a list,
the list will be returned untouched.
If arg is any other type of object,
it will be returned as a list
containing just the object.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
files = Split("f1.c f2.c f3.c")
files = env.Split("f4.c f5.c f6.c")
files = Split("""
	f7.c
	f8.c
	f9.c
""")
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-subst">
    <term>
      <literal>env.subst(input, [raw, target, source, conv])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Performs construction variable interpolation
on the specified string or sequence argument
<varname>input</varname>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
By default,
leading or trailing white space will
be removed from the result.
and all sequences of white space
will be compressed to a single space character.
Additionally, any
<literal>$(</literal>
and
<literal>$)</literal>
character sequences will be stripped from the returned string,
The optional
<varname>raw</varname>
argument may be set to
<literal>1</literal>
if you want to preserve white space and
<literal>$(</literal>-<literal>$)</literal>
sequences.
The
<varname>raw</varname>
argument may be set to
<literal>2</literal>
if you want to strip
all characters between
any
<literal>$(</literal>
and
<literal>$)</literal>
pairs
(as is done for signature calculation).
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the input is a sequence
(list or tuple),
the individual elements of
the sequence will be expanded,
and the results will be returned as a list.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The optional
<varname>target</varname>
and
<varname>source</varname>
keyword arguments
must be set to lists of
target and source nodes, respectively,
if you want the
<envar xmlns="http://www.scons.org/dbxsd/v1.0">$TARGET</envar>,
<envar xmlns="http://www.scons.org/dbxsd/v1.0">$TARGETS</envar>,
<envar xmlns="http://www.scons.org/dbxsd/v1.0">$SOURCE</envar>
and
<envar xmlns="http://www.scons.org/dbxsd/v1.0">$SOURCES</envar>
to be available for expansion.
This is usually necessary if you are
calling
<function xmlns="http://www.scons.org/dbxsd/v1.0">env.subst</function>
from within a Python function used
as an SCons action.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returned string values or sequence elements
are converted to their string representation by default.
The optional
<varname>conv</varname>
argument
may specify a conversion function
that will be used in place of
the default.
For example, if you want Python objects
(including SCons Nodes)
to be returned as Python objects,
you can use the Python
Λ
idiom to pass in an unnamed function
that simply returns its unconverted argument.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Example:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
print env.subst("The C compiler is: $CC")

def compile(target, source, env):
    sourceDir = env.subst("${SOURCE.srcdir}",
                          target=target,
                          source=source)

source_nodes = env.subst('$EXPAND_TO_NODELIST',
                         conv=lambda x: x)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Tag">
    <term>
      <literal>Tag(node, tags)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Annotates file or directory Nodes with
information about how the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="b-Package"><function>Package</function></link>
Builder should package those files or directories.
All tags are optional.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# makes sure the built library will be installed with 0644 file
# access mode
Tag( Library( 'lib.c' ), UNIX_ATTR="0644" )

# marks file2.txt to be a documentation file
Tag( 'file2.txt', DOC )
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-TargetSignatures">
    <term>
      <literal>TargetSignatures(type)</literal>
    </term>
    <term>
      <literal>env.TargetSignatures(type)</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note:  Although it is not yet officially deprecated,
use of this function is discouraged.
See the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-Decider"><function>Decider</function></link>
function for a more flexible and straightforward way
to configure SCons' decision-making.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">TargetSignatures</function>
function tells
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
how to decide if a target file
(a file that
<emphasis>is</emphasis>
built from any other files)
has changed since the last time it
was used to build some other target file.
Legal values are
<literal>"build"</literal>;
<literal>"content"</literal>
(or its synonym
<literal>"MD5"</literal>);
<literal>"timestamp"</literal>;
or
<literal>"source"</literal>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If the environment method is used,
the specified type of target signature is only used
for targets built with that environment.
If the global function is used,
the specified type of signature becomes the default
used for all target files that
don't have an explicit target signature type
specified for their environments.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>"content"</literal>
(or its synonym
<literal>"MD5"</literal>)
means
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
decides that a target file has changed
if the MD5 checksum of its contents has changed since
the last time it was used to rebuild some other target file.
This means
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will open up
MD5 sum the contents
of target files after they're built,
and may decide that it does not need to rebuild
"downstream" target files if a file was
rebuilt with exactly the same contents as the last time.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>"timestamp"</literal>
means
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
decides that a target file has changed
if its timestamp (modification time) has changed since
the last time it was used to rebuild some other target file.
(Note that although this is similar to the behavior of Make,
by default it will also rebuild if the dependency is
<emphasis>older</emphasis>
than the last time it was used to rebuild the target file.)
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>"source"</literal>
means
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
decides that a target file has changed
as specified by the corresponding
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceSignatures</function>
setting
(<literal>"MD5"</literal>
or
<literal>"timestamp"</literal>).
This means that
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
will treat all input files to a target the same way,
regardless of whether they are source files
or have been built from other files.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>"build"</literal>
means
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
decides that a target file has changed
if it has been rebuilt in this invocation
or if its content or timestamp have changed
as specified by the corresponding
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceSignatures</function>
setting.
This "propagates" the status of a rebuilt file
so that other "downstream" target files
will always be rebuilt,
even if the contents or the timestamp
have not changed.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<literal>"build"</literal>
signatures are fastest because
<literal>"content"</literal>
(or
<literal>"MD5"</literal>)
signatures take longer to compute,
but are more accurate than
<literal>"timestamp"</literal>
signatures,
and can prevent unnecessary "downstream" rebuilds
when a target file is rebuilt to the exact same contents
as the previous build.
The
<literal>"source"</literal>
setting provides the most consistent behavior
when other target files may be rebuilt from
both source and target input files.
The default value is
<literal>"source"</literal>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Because the default setting is
<literal>"source"</literal>,
using
<function xmlns="http://www.scons.org/dbxsd/v1.0">SourceSignatures</function>
is generally preferable to
<function xmlns="http://www.scons.org/dbxsd/v1.0">TargetSignatures</function>,
so that the up-to-date decision
will be consistent for all files
(or all files built with a specific construction environment).
Use of
<function xmlns="http://www.scons.org/dbxsd/v1.0">TargetSignatures</function>
provides specific control for how built target files
affect their "downstream" dependencies.
</para>
</listitem>
  </varlistentry>
  <varlistentry id="f-Tool">
    <term>
      <literal>Tool(string, [toolpath, **kw])</literal>
    </term>
    <term>
      <literal>env.Tool(string, [toolpath, **kw])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">Tool</function>
form of the function
returns a callable object
that can be used to initialize
a construction environment using the
tools keyword of the Environment() method.
The object may be called with a construction
environment as an argument,
in which case the object will
add the necessary variables
to the construction environment
and the name of the tool will be added to the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="cv-TOOLS"><envar>$TOOLS</envar></link>
construction variable.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Additional keyword arguments are passed to the tool's
<function>generate</function>()
method.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env = Environment(tools = [ Tool('msvc') ])

env = Environment()
t = Tool('msvc')
t(env)  # adds 'msvc' to the TOOLS variable
u = Tool('opengl', toolpath = ['tools'])
u(env)  # adds 'opengl' to the TOOLS variable
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The
<function xmlns="http://www.scons.org/dbxsd/v1.0">env.Tool</function>
form of the function
applies the callable object for the specified tool
<varname>string</varname>
to the environment through which the method was called.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Additional keyword arguments are passed to the tool's
<function>generate</function>()
method.
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env.Tool('gcc')
env.Tool('opengl', toolpath = ['build/tools'])
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-Value">
    <term>
      <literal>Value(value, [built_value])</literal>
    </term>
    <term>
      <literal>env.Value(value, [built_value])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Returns a Node object representing the specified Python value.  Value
Nodes can be used as dependencies of targets.  If the result of
calling
<function>str</function>(<varname>value</varname>)
changes between SCons runs, any targets depending on
<function>Value</function>(<varname>value</varname>)
will be rebuilt.
(This is true even when using timestamps to decide if
files are up-to-date.)
When using timestamp source signatures, Value Nodes'
timestamps are equal to the system time when the Node is created.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The returned Value Node object has a
<function>write</function>()
method that can be used to "build" a Value Node
by setting a new value.
The optional
<varname>built_value</varname>
argument can be specified
when the Value Node is created
to indicate the Node should already be considered
"built."
There is a corresponding
<function>read</function>()
method that will return the built value of the Node.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
env = Environment()

def create(target, source, env):
    # A function that will write a 'prefix=$SOURCE'
    # string into the file name specified as the
    # $TARGET.
    f = open(str(target[0]), 'wb')
    f.write('prefix=' + source[0].get_contents())

# Fetch the prefix= argument, if any, from the command
# line, and use /usr/local as the default.
prefix = ARGUMENTS.get('prefix', '/usr/local')

# Attach a .Config() builder for the above function action
# to the construction environment.
env['BUILDERS']['Config'] = Builder(action = create)
env.Config(target = 'package-config', source = Value(prefix))

def build_value(target, source, env):
    # A function that "builds" a Python Value by updating
    # the the Python value with the contents of the file
    # specified as the source of the Builder call ($SOURCE).
    target[0].write(source[0].get_contents())

output = env.Value('before')
input = env.Value('after')

# Attach a .UpdateValue() builder for the above function
# action to the construction environment.
env['BUILDERS']['UpdateValue'] = Builder(action = build_value)
env.UpdateValue(target = Value(output), source = Value(input))
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-VariantDir">
    <term>
      <literal>VariantDir(variant_dir, src_dir, [duplicate])</literal>
    </term>
    <term>
      <literal>env.VariantDir(variant_dir, src_dir, [duplicate])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Use the
<function xmlns="http://www.scons.org/dbxsd/v1.0">VariantDir</function>
function to create a copy of your sources in another location:
if a name under
<varname>variant_dir</varname>
is not found but exists under
<varname>src_dir</varname>,
the file or directory is copied to
<varname>variant_dir</varname>.
Target files can be built in a different directory
than the original sources by simply refering to the sources (and targets)
within the variant tree.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
<function xmlns="http://www.scons.org/dbxsd/v1.0">VariantDir</function>
can be called multiple times with the same
<varname>src_dir</varname>
to set up multiple builds with different options
(<varname>variants</varname>).
The
<varname>src_dir</varname>
location must be in or underneath the SConstruct file's directory, and
<varname>variant_dir</varname>
may not be underneath
<varname>src_dir</varname>.
<!--
TODO: Can the above restrictions be clarified or relaxed?
TODO: The latter restriction is clearly not completely right;
TODO: src_dir = '.' works fine with a build dir under it.
-->
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
The default behavior is for
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to physically duplicate the source files in the variant tree.
Thus, a build performed in the variant tree is guaranteed to be identical
to a build performed in the source tree even if
intermediate source files are generated during the build,
or preprocessors or other scanners search for included files
relative to the source file,
or individual compilers or other invoked tools are hard-coded
to put derived files in the same directory as source files.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
If possible on the platform,
the duplication is performed by linking rather than copying;
see also the
<option>--duplicate</option>
command-line option.
Moreover, only the files needed for the build are duplicated;
files and directories that are not used are not present in
<varname>variant_dir</varname>.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Duplicating the source tree may be disabled by setting the
<literal>duplicate</literal>
argument to
<literal>0</literal>
(zero).
This will cause
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
to invoke Builders using the path names of source files in
<varname>src_dir</varname>
and the path names of derived files within
<varname>variant_dir</varname>.
This is always more efficient than
<literal>duplicate=1</literal>,
and is usually safe for most builds
(but see above for cases that may cause problems).
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Note that
<function xmlns="http://www.scons.org/dbxsd/v1.0">VariantDir</function>
works most naturally with a subsidiary SConscript file.
However, you would then call the subsidiary SConscript file
not in the source directory, but in the
<varname>variant_dir</varname>,
regardless of the value of
<literal>duplicate</literal>.
This is how you tell
<filename xmlns="http://www.scons.org/dbxsd/v1.0">scons</filename>
which variant of a source tree to build:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# run src/SConscript in two variant directories
VariantDir('build/variant1', 'src')
SConscript('build/variant1/SConscript')
VariantDir('build/variant2', 'src')
SConscript('build/variant2/SConscript')
</example_commands>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
See also the
<link xmlns="http://www.scons.org/dbxsd/v1.0" linkend="f-SConscript"><function>SConscript</function></link>
function, described above,
for another way to specify a variant directory
in conjunction with calling a subsidiary SConscript file.
</para>

<para xmlns="http://www.scons.org/dbxsd/v1.0">
Examples:
</para>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# use names in the build directory, not the source directory
VariantDir('build', 'src', duplicate=0)
Program('build/prog', 'build/source.c')
</example_commands>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# this builds both the source and docs in a separate subtree
VariantDir('build', '.', duplicate=0)
SConscript(dirs=['build/src','build/doc'])
</example_commands>

<example_commands xmlns="http://www.scons.org/dbxsd/v1.0">
# same as previous example, but only uses SConscript
SConscript(dirs='src', variant_dir='build/src', duplicate=0)
SConscript(dirs='doc', variant_dir='build/doc', duplicate=0)
</example_commands>
</listitem>
  </varlistentry>
  <varlistentry id="f-WhereIs">
    <term>
      <literal>WhereIs(program, [path, pathext, reject])</literal>
    </term>
    <term>
      <literal>env.WhereIs(program, [path, pathext, reject])</literal>
    </term>
    <listitem>
<para xmlns="http://www.scons.org/dbxsd/v1.0">
Searches for the specified executable
<varname>program</varname>,
returning the full path name to the program
if it is found,
and returning None if not.
Searches the specified
<varname>path</varname>,
the value of the calling environment's PATH
(<literal>env['ENV']['PATH']</literal>),
or the user's current external PATH
(<literal>os.environ['PATH']</literal>)
by default.
On Windows systems, searches for executable
programs with any of the file extensions
listed in the specified
<varname>pathext</varname>,
the calling environment's PATHEXT
(<literal>env['ENV']['PATHEXT']</literal>)
or the user's current PATHEXT
(<literal>os.environ['PATHEXT']</literal>)
by default.
Will not select any
path name or names
in the specified
<varname>reject</varname>
list, if any.
</para>
</listitem>
  </varlistentry>
</variablelist>