path: root/src/engine/SCons/Action.xml

<?xml version="1.0"?>
<!--
__COPYRIGHT__

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">

<cvar name="IMPLICIT_COMMAND_DEPENDENCIES">
<summary>
<para>
Controls whether or not SCons will
add implicit dependencies for the commands
executed to build targets.
</para>

<para>
By default, SCons will add
to each target
an implicit dependency on the command
represented by the first argument of any
command line it executes (which is typically
the command itself). By setting such
a dependency, &SCons; can determine that
a target should be rebuilt if the command changes,
such as when a compiler is upgraded to a new version.
The specific file for the dependency is
found by searching the
<varname>PATH</varname>
variable in the
<varname>ENV</varname> dictionary
in the &consenv; used to execute the command.
The default is the same as
setting the &consvar;
&cv-IMPLICIT_COMMAND_DEPENDENCIES;
to a True-like value (<quote>true</quote>,
<quote>yes</quote>,
or <quote>1</quote> - but not a number
greater than one, as that has a different meaning).
</para>

<para>
Action strings can be segmented by the
use of an AND operator, <literal>&amp;&amp;</literal>.
In a segemented string, each segment is a separate
<quote>command line</quote>, these are run
sequentially until one fails or the entire
sequence has been executed. If an
action string is segmented, then the selected
behavior of &cv-IMPLICIT_COMMAND_DEPENDENCIES;
is applied to each segment.
</para>

<para>
If &cv-IMPLICIT_COMMAND_DEPENDENCIES;
is set to a False-like value
(<quote>none</quote>,
<quote>false</quote>,
<quote>no</quote>,
<quote>0</quote>,
etc.),
then the implicit dependency will
not be added to the targets
built with that &consenv;.
</para>

<para>
If &cv-IMPLICIT_COMMAND_DEPENDENCIES;
is set to <quote>2</quote> or higher,
then that number of arguments in the command line
will be scanned for relative or absolute paths.
If any are present, they will be added as
implicit dependencies to the targets built
with that &consenv;.
The first argument in the command line will be
searched for using the <varname>PATH</varname>
variable in the <varname>ENV</varname> dictionary
in the &consenv; used to execute the command.
The other arguments will only be found if they
are absolute paths or valid paths relative
to the working directory.
</para>

<para>
If &cv-IMPLICIT_COMMAND_DEPENDENCIES;
is set to <quote>all</quote>,
then all arguments in the command line will be
scanned for relative or absolute paths.
If any are present, they will be added as
implicit dependencies to the targets built
with that &consenv;.
The first argument in the command line will be
searched for using the <varname>PATH</varname>
variable in the <varname>ENV</varname> dictionary
in the &consenv; used to execute the command.
The other arguments will only be found if they
are absolute paths or valid paths relative
to the working directory.
</para>

<example_commands>
env = Environment(IMPLICIT_COMMAND_DEPENDENCIES=False)
</example_commands>
</summary>
</cvar>

<cvar name="PRINT_CMD_LINE_FUNC">
<summary>
<para>
A Python function used to print the command lines as they are executed
(assuming command printing is not disabled by the
<option>-q</option>
or
<option>-s</option>
options or their equivalents).
The function should take four arguments:
<varname>s</varname>,
the command being executed (a string),
<varname>target</varname>,
the target being built (file node, list, or string name(s)),
<varname>source</varname>,
the source(s) used (file node, list, or string name(s)), and
<varname>env</varname>,
the environment being used.
</para>

<para>
The function must do the printing itself.  The default implementation,
used if this variable is not set or is None, is:
</para>
<example_commands>
def print_cmd_line(s, target, source, env):
  sys.stdout.write(s + "\n")
</example_commands>

<para>
Here's an example of a more interesting function:
</para>

<example_commands>
def print_cmd_line(s, target, source, env):
   sys.stdout.write("Building %s -> %s...\n" %
    (' and '.join([str(x) for x in source]),
     ' and '.join([str(x) for x in target])))
env=Environment(PRINT_CMD_LINE_FUNC=print_cmd_line)
env.Program('foo', 'foo.c')
</example_commands>

<para>
This just prints "Building <varname>targetname</varname> from <varname>sourcename</varname>..." instead
of the actual commands.
Such a function could also log the actual commands to a log file,
for example.
</para>
</summary>
</cvar>

<cvar name="SPAWN">
<summary>
<para>
A command interpreter function that will be called to execute command line
strings. The function must expect the following arguments:
</para>

<example_commands>
def spawn(shell, escape, cmd, args, env):
</example_commands>

<para>
<varname>sh</varname>
is a string naming the shell program to use.
<varname>escape</varname>
is a function that can be called to escape shell special characters in
the command line.
<varname>cmd</varname>
is the path to the command to be executed.
<varname>args</varname>
is the arguments to the command.
<varname>env</varname>
is a dictionary of the environment variables
in which the command should be executed.
</para>
</summary>
</cvar>

</sconsdoc>