path: root/src/engine/SCons/Script/Main.xml

<?xml version="1.0"?>
<!--
Copyright (c) 2001 - 2019 The SCons Foundation

This file is processed by the bin/SConsDoc.py module.
See its __doc__ string for a discussion of the format.
-->

<!DOCTYPE sconsdoc [
<!ENTITY % scons SYSTEM '../../../../doc/scons.mod'>
%scons;
<!ENTITY % builders-mod SYSTEM '../../../../doc/generated/builders.mod'>
%builders-mod;
<!ENTITY % functions-mod SYSTEM '../../../../doc/generated/functions.mod'>
%functions-mod;
<!ENTITY % tools-mod SYSTEM '../../../../doc/generated/tools.mod'>
%tools-mod;
<!ENTITY % variables-mod SYSTEM '../../../../doc/generated/variables.mod'>
%variables-mod;
]>

<sconsdoc 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">


<scons_function name="AddOption">
<arguments signature="global">
(arguments)
</arguments>
<summary>
<para>
This function adds a new command-line option to be recognized.
The specified
<varname>arguments</varname>
are the same as supported by the <function>add_option</function>
method in the standard Python library module <emphasis>optparse</emphasis>,
with a few additional capabilities noted below;
see the documentation for
<emphasis>optparse</emphasis>
for a thorough discussion of its option-processing capabities.
</para>

<para>
In addition to the arguments and values supported by the
<function>optparse.add_option</function>()
method,
the SCons
&f-AddOption;
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
&f-AddOption;
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>
If no
<literal>default=</literal>
keyword argument is supplied when calling
&f-AddOption;,
the option will have a default value of
<literal>None</literal>.
</para>

<para>
Unlike regular <emphasis>optparse</emphasis>, option names
added via <function>AddOption</function> must be matched
exactly, the automatic matching of abbreviations on the
command line for long options is not supported.
To allow specific abbreviations,
include them in the &f-AddOption; call.
</para>

<para>
Once a new command-line option has been added with
&f-AddOption;,
the option value may be accessed using
&f-GetOption;
or
<function>env.GetOption</function>().
<!--
The value may also be set, using
&f-SetOption;
or
<function>env.SetOption</function>(),
if conditions in a
&SConscript;
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.
-->
&f-SetOption; is not currently supported for
options added with &f-AddOption;.
</para>

<para>
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
&f-AddOption;
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
&f-AddOption;
calls occur.
</para>

<para>
Example:
</para>

<example_commands>
AddOption('--prefix',
          dest='prefix',
          nargs=1, type='string',
          action='store',
          metavar='DIR',
          help='installation prefix')
env = Environment(PREFIX = GetOption('prefix'))
</example_commands>

<note>
<para>
While &AddOption; behaves like
<function>add_option</function>,
from the <emphasis>optparse</emphasis> module,
the behavior of options added by &AddOption;
which take arguments is underfined in
<command>scons</command> if whitespace
(rather than an <literal>=</literal> sign) is used as
the separator on the command line when
the option is invoked.
Such usage should be avoided.
</para>
</note>

</summary>
</scons_function>

<scons_function name="GetBuildFailures">
<arguments signature="global">
()
</arguments>
<summary>
<para>
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>
<literal>.node</literal>
The node that was being built
when the build failure occurred.
</para>

<para>
<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>
<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>
<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>
<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>
<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>
<literal>.command</literal>
The actual expanded command that was executed and failed,
after expansion of
&cv-link-TARGET;,
&cv-link-SOURCE;,
and other construction variables.
</para>

<para>
Note that the
&f-GetBuildFailures;
function
will always return an empty list
until any build failure has occurred,
which means that
&f-GetBuildFailures;
will always return an empty list
while the
&SConscript;
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>
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>
</summary>
</scons_function>

<scons_function name="GetOption">
<arguments>
(name)
</arguments>
<summary>
<para>
This function provides a way to query the value of
SCons options set on scons command line
(or set using the
&f-link-SetOption;
function).
The options supported are:
</para>

<para>
<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>
See the documentation for the
corresponding command line object for information about each specific
option.
</para>
</summary>
</scons_function>

<scons_function name="Progress">
<arguments signature="global">
(callable, [interval])
</arguments>
<arguments signature="global">
(string, [interval, file, overwrite])
</arguments>
<arguments signature="global">
(list_of_strings, [interval, file, overwrite])
</arguments>
<summary>
<para>
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>
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>
An example of a simple custom progress function
that prints a string containing the Node name
every 10 Nodes:
</para>

<example_commands>
def my_progress_function(node, *args, **kw):
    print('Evaluating node %s!' % node)
Progress(my_progress_function, interval=10)
</example_commands>

<para>
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>
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>
If the first argument
&f-link-Progress;
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>
import sys
Progress('.', interval=100, file=sys.stderr)
</example_commands>

<para>
If the string contains the verbatim substring
&cv-TARGET;,
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>
import sys
Progress('$TARGET\r', overwrite=True)
</example_commands>

<para>
If the first argument to
&f-Progress;
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>
Progress(['-\r', '\\\r', '|\r', '/\r'], interval=5)
</example_commands>
</summary>
</scons_function>

<scons_function name="Precious">
<arguments>
(target, ...)
</arguments>
<summary>
<para>
Marks each given
<varname>target</varname>
as precious so it is not deleted before it is rebuilt. Normally
&scons;
deletes a target before building it.
Multiple targets can be passed in to a single call to
&f-Precious;.
</para>
</summary>
</scons_function>

<scons_function name="Pseudo">
<arguments>
(target, ...)
</arguments>
<summary>
<para>
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
&f-Alias;
is more appropriate.

Multiple targets can be passed in to a single call to
&f-Pseudo;.
</para>
</summary>
</scons_function>
<scons_function name="SetOption">
<arguments>
(name, value)
</arguments>
<summary>
<para>
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>
<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>
See the documentation for the
corresponding command line object for information about each specific
option.
</para>

<para>
Example:
</para>

<example_commands>
SetOption('max_drift', 1)
</example_commands>
</summary>
</scons_function>

</sconsdoc>