path: root/SCons/Script/Main.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">


<scons_function name="AddOption">
<arguments signature="global">
(arguments)
</arguments>
<summary>
<para>
Adds a local (project-specific) command-line option.
<parameter>arguments</parameter>
are the same as those supported by the <function>add_option</function>
method in the standard Python library module <systemitem>optparse</systemitem>,
with a few additional capabilities noted below.
See the documentation for
<systemitem>optparse</systemitem>
for a thorough discussion of its option-processing capabities.
</para>

<para>
In addition to the arguments and values supported by the
<systemitem>optparse</systemitem>
<function>add_option</function>
method, &f-AddOption;
allows setting the
<parameter>nargs</parameter>
keyword value to
a string consisting of a question mark
(<literal>'?'</literal>)
to indicate that the option argument for
that option string is optional.
If the option string is present on the
command line but has no matching option
argument, the value of the
<parameter>const</parameter>
keyword argument is produced as the value
of the option.
If the option string is omitted from
the command line, the value of the
<parameter>default</parameter>
keyword argument is produced, as usual;
if there is no
<parameter>default</parameter>
keyword argument in the &f-AddOption; call,
<constant>None</constant> is produced.
</para>

<para>
<systemitem>optparse</systemitem> recognizes
abbreviations of long option names,
as long as they can be unambiguously resolved.
For example, if
<function>add_option</function> is called to
define a <option>--devicename</option> option,
it will recognize <option>--device</option>,
<option>--dev</option>
and so forth as long as there is no other option
which could also match to the same abbreviation.
Options added via
&f-AddOption; do not support
the automatic recognition of abbreviations.
Instead, to allow specific abbreviations,
include them as synonyms in the &f-AddOption; call itself.
</para>

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

<para>
Help text for an option is a combination
of the string supplied in the
<parameter>help</parameter> keyword
argument to &f-AddOption; and information
collected from the other keyword arguments.
Such help is displayed if the
<option>-h</option> command line option
is used (but not with <option>-H</option>).
Help for all local options is displayed
under the separate heading
<emphasis role="bold">Local Options</emphasis>.
The options are unsorted - they 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>

<para>For that example,
the following help text would be produced:</para>

<screen>
Local Options:
  --prefix=DIR                installation prefix
</screen>

<para>
Help text for local options may be unavailable if
the &f-link-Help; function has been called,
see the &f-Help; documentation for details.
</para>

<note>
<para>
As an artifact of the internal implementation,
the behavior of options added by &AddOption;
which take option arguments is undefined
<emphasis>if</emphasis> whitespace
(rather than an <literal>=</literal> sign) is used as
the separator on the command line.
Users should avoid such usage; it is recommended
to add a note to this effect to project documentation
if the situation is likely to arise.
In addition, if the <parameter>nargs</parameter>
keyword is used to specify more than one following
option argument (that is, with a value of <constant>2</constant>
or greater), such arguments would necessarily
be whitespace separated, triggering the issue.
Developers should not use &AddOption; this way.
Future versions of &SCons; will likely forbid such usage.
</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 <option>--cache-debug</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>cache_disable</literal></term>
<listitem>
<para>
which corresponds to <option>--cache-disable</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>cache_force</literal></term>
<listitem>
<para>
which corresponds to <option>--cache-force</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>cache_show</literal></term>
<listitem>
<para>
which corresponds to <option>--cache-show</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>clean</literal></term>
<listitem>
<para>
which corresponds to <option>-c</option>, <option>--clean</option>
and <option>--remove</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>config</literal></term>
<listitem>
<para>
which corresponds to <option>--config</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>directory</literal></term>
<listitem>
<para>
which corresponds to <option>-C</option> and <option>--directory</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>diskcheck</literal></term>
<listitem>
<para>
which corresponds to <option>--diskcheck</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>duplicate</literal></term>
<listitem>
<para>
which corresponds to <option>--duplicate</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>file</literal></term>
<listitem>
<para>
which corresponds to <option>-f</option>, <option>--file</option>, <option>--makefile</option> and <option>--sconstruct</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>help</literal></term>
<listitem>
<para>
which corresponds to <option>-h</option> and <option>--help</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ignore_errors</literal></term>
<listitem>
<para>
which corresponds to <option>--ignore-errors</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>implicit_cache</literal></term>
<listitem>
<para>
which corresponds to <option>--implicit-cache</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>implicit_deps_changed</literal></term>
<listitem>
<para>
which corresponds to <option>--implicit-deps-changed</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>implicit_deps_unchanged</literal></term>
<listitem>
<para>
which corresponds to <option>--implicit-deps-unchanged</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>interactive</literal></term>
<listitem>
<para>
which corresponds to <option>--interact</option> and <option>--interactive</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>keep_going</literal></term>
<listitem>
<para>
which corresponds to <option>-k</option> and <option>--keep-going</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>max_drift</literal></term>
<listitem>
<para>
which corresponds to <option>--max-drift</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>no_exec</literal></term>
<listitem>
<para>
which corresponds to <option>-n</option>,
<option>--no-exec</option>, <option>--just-print</option>,
<option>--dry-run</option> and <option>--recon</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>no_site_dir</literal></term>
<listitem>
<para>
which corresponds to <option>--no-site-dir</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>num_jobs</literal></term>
<listitem>
<para>
which corresponds to <option>-j</option> and <option>--jobs</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>profile_file</literal></term>
<listitem>
<para>
which corresponds to <option>--profile</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>question</literal></term>
<listitem>
<para>
which corresponds to <option>-q</option> and <option>--question</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>random</literal></term>
<listitem>
<para>
which corresponds to <option>--random</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>repository</literal></term>
<listitem>
<para>
which corresponds to <option>-Y</option>, <option>--repository</option> and <option>--srcdir</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>silent</literal></term>
<listitem>
<para>
which corresponds to <option>-s</option>, <option>--silent</option> and <option>--quiet</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>site_dir</literal></term>
<listitem>
<para>
which corresponds to <option>--site-dir</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>stack_size</literal></term>
<listitem>
<para>
which corresponds to <option>--stack-size</option>;
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>taskmastertrace_file</literal></term>
<listitem>
<para>
which corresponds to <option>--taskmastertrace</option>; and
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>warn</literal></term>
<listitem>
<para>
which corresponds to <option>--warn</option> and <option>--warning</option>.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>

<para>
See the documentation for the
corresponding command line option 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
<methodname>__call__</methodname> method),
the function will be called
once every
<varname>interval</varname>
times a Node is evaluated (default <constant>1</constant>).
The callable will be passed the evaluated Node
as its only argument.
(For future compatibility,
it's a good idea to also add
<parameter>*args</parameter>
and
<parameter>**kwargs</parameter>
as arguments to your function or method signatures.
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, **kwargs):
    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 to
&f-Progress; is a string or list of strings,
it is taken as text to be displayed every
<varname>interval</varname>
evaluated Nodes.
If the first argument is a list of strings,
then each string in the list will be displayed
in rotating fashion every
<varname>interval</varname>
evaluated Nodes.
</para>

<para>
The default is to print the string on standard output.
An alternate output stream
may be specified with the
<parameter>file</parameter>
keyword argument, which the
caller must pass already opened.
</para>

<para>
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
<literal>$TARGET;</literal>,
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 carriage return)
(<literal>\r</literal>)
to cause each line to overwritten by the next line,
and the
<parameter>overwrite</parameter>
keyword argument (default <literal>False</literal>)
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>
A list of strings can be used to implement a "spinner"
on the user's screen as follows, changing every
five evaluated Nodes:
</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>
Sets &scons; option variable <parameter>name</parameter>
to <parameter>value</parameter>.
These options are all also settable via
&scons; command-line options but the variable name
may differ from the command-line option name (see table).
A value set via command-line option will take
precedence over one set with &f-SetOption;, which
allows setting a project default in the scripts and
temporarily overriding it via command line.
Options which affect the reading and processing of SConscript files
are not settable this way, since those files must
be read in order to find the &f-SetOption; call.
</para>

<para>
The settable variables with their associated command-line options are:
</para>

<!-- UPDATE_SETOPTION_DOCS -->
<!-- This list comes directly from SConsValues.settable. Keep in sync. -->

<informaltable rowsep="1" colsep="1" frame="topbot">
<tgroup cols="2">
<thead>
<row><entry>Variable</entry><entry>Command-line options</entry></row>
</thead>
<tbody>
<row><entry>
<varname>clean</varname>
</entry><entry>
<option>-c</option>, <option>--clean</option>, <option>--remove</option>
</entry></row>
<row><entry>
<varname>diskcheck</varname>
</entry><entry>
<option>--diskcheck</option>
</entry></row>
<row><entry>
<varname>duplicate</varname>
</entry><entry>
<option>--duplicate</option>
</entry></row>
<row><entry>
<varname>help</varname>
</entry><entry>
<option>-h</option>, <option>--help</option>
</entry></row>
<row><entry>
<varname>implicit_cache</varname>
</entry><entry>
<option>--implicit-cache</option>
</entry></row>
<!--TODO: add implicit-deps-changed, implicit-deps-unchanged ? -->
<row><entry>
<varname>max_drift</varname>
</entry><entry>
<option>--max-drift</option>
</entry></row>
<row><entry>
<varname>md5_chunksize</varname>
</entry><entry>
<option>--md5-chunksize</option>
</entry></row>
<row><entry>
<varname>no_exec</varname>
</entry><entry>
<option>-n</option>, <option>--no-exec</option>,
<option>--just-print</option>, <option>--dry-run</option>,
<option>--recon</option>
</entry></row>
<row><entry>
<varname>no_progress</varname>
</entry><entry>
<option>-Q</option>
</entry></row>
<row><entry>
<varname>num_jobs</varname>
</entry><entry>
<option>-j</option>, <option>--jobs</option>
</entry></row>
<row><entry>
<varname>random</varname>
</entry><entry>
<option>--random</option>
</entry></row>
<row><entry>
<varname>silent</varname>
</entry><entry>
<option>--silent</option>.
</entry></row>
<row><entry>
<varname>stack_size</varname>
</entry><entry>
<option>--stack-size</option>
</entry></row>
<row><entry>
<varname>warn</varname>
</entry><entry>
<option>--warn</option>.
</entry></row>
</tbody>
</tgroup>
</informaltable>

<para>
See the documentation in the manpage for the
corresponding command line option for information about each specific option.
Option values which are boolean in nature (that is, they are
either on or off) should be set to a true value (<constant>True</constant>,
<constant>1</constant>) or a false value (<constant>False</constant>,
<constant>0</constant>).
</para>

<note>
<para>
If <varname>no_progress</varname> is set via &f-SetOption;
there will still be initial progress output as &SCons; has
to start reading SConscript files before it can see the
&f-SetOption; in an SConscript file:
<computeroutput>scons: Reading SConscript files ...</computeroutput>
</para>
</note>

<para>
Example:
</para>

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

</sconsdoc>