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<!--

  Copyright (c) 2001, 2002, 2003 Steven Knight

  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,
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  in all copies or substantial portions of the Software.

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  KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
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  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 &Program;, &Object;, etc.),
  but takes as an additional argument
  the command to be executed to build the file:

  </para>

  <programlisting>
     env = Environment()
     env.Command('foo.out', 'foo.in', "sed 's/x/y/' &lt; $SOURCE &gt; $TARGET")
  </programlisting>

  <literallayout>
    % <userinput>scons -Q</userinput>
    sed 's/x/y/' < foo.in > foo.out
  </literallayout>

  <para>

  This is often more convenient than
  creating a &Builder; object
  and adding it to the &BUILDERS; variable
  of a &consenv;

  </para>

  <para>

  Note that the action you 

  </para>

  <programlisting>
     env = Environment()
     def build(target, source, env):
         # Whatever it takes to build
         return None
     env.Command('foo.out', 'foo.in', build)
  </programlisting>

  <literallayout>
    % <userinput>scons -Q</userinput>
    build("foo.out", "foo.in")
  </literallayout>