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+<!--
+
+ Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 The SCons Foundation
+
+ Permission is hereby granted, free of charge, to any person obtaining
+ a copy of this software and associated documentation files (the
+ "Software"), to deal in the Software without restriction, including
+ without limitation the rights to use, copy, modify, merge, publish,
+ distribute, sublicense, and/or sell copies of the Software, and to
+ permit persons to whom the Software is furnished to do so, subject to
+ the following conditions:
+
+ The above copyright notice and this permission notice shall be included
+ in all copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+ KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+ WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+-->
+
+ <!--
+
+ =head2 The C<Command> method
+
+
+ The C<Command> method is called as follows:
+
+ Command $env <target>, <inputs>, <build action>;
+
+ The target is made dependent upon the list of input files specified, and the
+ inputs must be built successfully or Cons will not attempt to build the
+ target.
+
+ To specify a command with multiple targets, you can specify a reference to a
+ list of targets. In Perl, a list reference can be created by enclosing a
+ list in square brackets. Hence the following command:
+
+ Command $env ['foo.h', 'foo.c'], 'foo.template', q(
+ gen %1
+ );
+
+ could be used in a case where the command C<gen> creates two files, both
+ F<foo.h> and F<foo.c>.
+
+ -->
+
+ <para>
+
+ Creating a &Builder; and attaching it to a &consenv;
+ allows for a lot of flexibility when you
+ want to re-use actions
+ to build multiple files of the same type.
+ This can, however, be cumbersome
+ if you only need to execute one specific command
+ to build a single file (or group of files).
+ For these situations, &SCons; supports a
+ &Command; &Builder; that arranges
+ for a specific action to be executed
+ to build a specific file or files.
+ This looks a lot like the other builders
+ (like &b-link-Program;, &b-link-Object;, etc.),
+ but takes as an additional argument
+ the command to be executed to build the file:
+
+ </para>
+
+ <scons_example name="ex1">
+ <file name="SConstruct" printme="1">
+ env = Environment()
+ env.Command('foo.out', 'foo.in', "sed 's/x/y/' < $SOURCE > $TARGET")
+ </file>
+ <file name="foo.in">
+ foo.in
+ </file>
+ </scons_example>
+
+ <para>
+
+ When executed,
+ &SCons; runs the specified command,
+ substituting &cv-link-SOURCE; and &cv-link-TARGET;
+ as expected:
+
+ </para>
+
+ <scons_output example="ex1">
+ <scons_output_command>scons -Q</scons_output_command>
+ </scons_output>
+
+ <para>
+
+ This is often more convenient than
+ creating a &Builder; object
+ and adding it to the &cv-link-BUILDERS; variable
+ of a &consenv;
+
+ </para>
+
+ <para>
+
+ Note that the action you specify to the
+ &Command; &Builder; can be any legal &SCons; &Action;,
+ such as a Python function:
+
+ </para>
+
+ <scons_example name="ex2">
+ <file name="SConstruct" printme="1">
+ env = Environment()
+ def build(target, source, env):
+ # Whatever it takes to build
+ return None
+ env.Command('foo.out', 'foo.in', build)
+ </file>
+ <file name="foo.in">
+ foo.in
+ </file>
+ </scons_example>
+
+ <para>
+
+ Which executes as follows:
+
+ </para>
+
+ <scons_output example="ex2">
+ <scons_output_command>scons -Q</scons_output_command>
+ </scons_output>
+
+ <para>
+
+ Note that &cv-link-SOURCE; and &cv-link-TARGET; are expanded
+ in the source and target as well as of SCons 1.1,
+ so you can write:
+
+ </para>
+
+ <scons_example name="ex3">
+ <file name="SConstruct" printme="1">
+ env.Command('${SOURCE.basename}.out', 'foo.in', build)
+ </file>
+ </scons_example>
+
+
+ <para>
+
+ which does the same thing as the previous example, but allows you
+ to avoid repeating yourself.
+
+ </para>
+