%scons; %builders-mod; %functions-mod; %tools-mod; %variables-mod; ]>

A dictionary mapping the names of the builders available through the &consenv; to underlying Builder objects. Custom builders need to be added to this to make them available. A platform-dependent default list of builders such as &b-link-Program;, &b-link-Library; etc. is used to populate this &consvar; when the &consenv; is initialized via the presence/absence of the tools those builders depend on. &cv-BUILDERS; can be examined to learn which builders will actually be available at run-time. Note that if you initialize this &consvar; through assignment when the &consenv; is created, that value for &cv-BUILDERS; will override any defaults: bld = Builder(action='foobuild < $SOURCE > $TARGET') env = Environment(BUILDERS={'NewBuilder': bld}) To instead use a new Builder object in addition to the default Builders, add your new Builder object like this: env = Environment() env.Append(BUILDERS={'NewBuilder': bld}) or this: env = Environment() env['BUILDERS']['NewBuilder'] = bld

A dictionary of environment variables to use when invoking commands. When &cv-ENV; is used in a command all list values will be joined using the path separator and any other non-string values will simply be coerced to a string. Note that, by default, &scons; does not propagate the environment in effect when you execute &scons; to the commands used to build target files. This is so that builds will be guaranteed repeatable regardless of the environment variables set at the time &scons; is invoked. If you want to propagate your environment variables to the commands executed to build target files, you must do so explicitly: import os env = Environment(ENV=os.environ.copy()) Note that you can choose only to propagate certain environment variables. A common example is the system PATH environment variable, so that &scons; uses the same utilities as the invoking shell (or other process): import os env = Environment(ENV={'PATH': os.environ['PATH']})

A list of the available implicit dependency scanners. New file scanners may be added by appending to this list, although the more flexible approach is to associate scanners with a specific Builder. See the manpage sections "Builder Objects" and "Scanner Objects" for more information.

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A reserved variable name that may not be set or used in a construction environment. (See the manpage section "Variable Substitution" for more information).

A list of the names of the Tool specifications that are part of this construction environment.

(action, [cmd/str/fun, [var, ...]] [option=value, ...])

A factory function to create an Action object for the specified action. See the manpage section "Action Objects" for a complete explanation of the arguments and behavior. Note that the &f-env-Action; form of the invocation will expand construction variables in any argument strings, including the action argument, at the time it is called using the construction variables in the env construction environment through which &f-env-Action; was called. The &f-Action; global function form delays all variable expansion until the Action object is actually used.

(object, function, [name]) (function, [name])

Adds function to an object as a method. function will be called with an instance object as the first argument as for other methods. If name is given, it is used as the name of the new method, else the name of function is used. When the global function &f-AddMethod; is called, the object to add the method to must be passed as the first argument; typically this will be &Environment;, in order to create a method which applies to all &consenvs; subsequently constructed. When called using the &f-env-AddMethod; form, the method is added to the specified &consenv; only. Added methods propagate through &f-env-Clone; calls. Examples: # Function to add must accept an instance argument. # The Python convention is to call this 'self'. def my_method(self, arg): print("my_method() got", arg) # Use the global function to add a method to the Environment class: AddMethod(Environment, my_method) env = Environment() env.my_method('arg') # Use the optional name argument to set the name of the method: env.AddMethod(my_method, 'other_method_name') env.other_method_name('another arg')

(target, action)

Arranges for the specified action to be performed after the specified target has been built. The specified action(s) may be an Action object, or anything that can be converted into an Action object See the manpage section "Action Objects" for a complete explanation. When multiple targets are supplied, the action may be called multiple times, once after each action that generates one or more targets in the list.

(target, action)

Arranges for the specified action to be performed before the specified target is built. The specified action(s) may be an Action object, or anything that can be converted into an Action object See the manpage section "Action Objects" for a complete explanation. When multiple targets are specified, the action(s) may be called multiple times, once before each action that generates one or more targets in the list. Note that if any of the targets are built in multiple steps, the action will be invoked just before the "final" action that specifically generates the specified target(s). For example, when building an executable program from a specified source .c file via an intermediate object file: foo = Program('foo.c') AddPreAction(foo, 'pre_action') The specified pre_action would be executed before &scons; calls the link command that actually generates the executable program binary foo, not before compiling the foo.c file into an object file.

(alias, [targets, [action]])

Creates one or more phony targets that expand to one or more other targets. An optional action (command) or list of actions can be specified that will be executed whenever the any of the alias targets are out-of-date. Returns the Node object representing the alias, which exists outside of any file system. This Node object, or the alias name, may be used as a dependency of any other target, including another alias. &f-Alias; can be called multiple times for the same alias to add additional targets to the alias, or additional actions to the list for this alias. Aliases are global even if set through the construction environment method. Examples: Alias('install') Alias('install', '/usr/bin') Alias(['install', 'install-lib'], '/usr/local/lib') env.Alias('install', ['/usr/local/bin', '/usr/local/lib']) env.Alias('install', ['/usr/local/man']) env.Alias('update', ['file1', 'file2'], "update_database $SOURCES")

(target, ...)

Marks each given target so that it is always assumed to be out of date, and will always be rebuilt if needed. Note, however, that &f-AlwaysBuild; does not add its target(s) to the default target list, so the targets will only be built if they are specified on the command line, or are a dependent of a target specified on the command line--but they will always be built if so specified. Multiple targets can be passed in to a single call to &f-AlwaysBuild;.

(key=val, [...])

Intelligently append values to &consvars; in the &consenv; named by env. The &consvars; and values to add to them are passed as key=val pairs (Python keyword arguments). &f-env-Append; is designed to allow adding values without normally having to know the data type of an existing &consvar;. Regular Python syntax can also be used to manipulate the &consvar;, but for that you must know the type of the &consvar;: for example, different Python syntax is needed to combine a list of values with a single string value, or vice versa. Some pre-defined &consvars; do have type expectations based on how &SCons; will use them, for example &cv-link-CPPDEFINES; is normally a string or a list of strings, but can be a string, a list of strings, a list of tuples, or a dictionary, while &cv-link-LIBEMITTER; would expect a callable or list of callables, and &cv-link-BUILDERS; would expect a mapping type. Consult the documentation for the various &consvars; for more details. The following descriptions apply to both the append and prepend functions, the only difference being the insertion point of the added values. If env. does not have a &consvar; indicated by key, val is added to the environment under that key as-is. val can be almost any type, and &SCons; will combine it with an existing value into an appropriate type, but there are a few special cases to be aware of. When two strings are combined, the result is normally a new string, with the caller responsible for supplying any needed separation. The exception to this is the &consvar; &cv-link-CPPDEFINES;, in which each item will be postprocessed by adding a prefix and/or suffix, so the contents are treated as a list of strings, that is, adding a string will result in a separate string entry, not a combined string. For &cv-CPPDEFINES; as well as for &cv-link-LIBS;, and the various *PATH variables, &SCons; will supply the compiler-specific syntax (e.g. adding a -D or /D prefix for &cv-CPPDEFINES;), so this syntax should be omitted when adding values to these variables. Example (gcc syntax shown in the expansion of &CPPDEFINES;): env = Environment(CXXFLAGS="-std=c11", CPPDEFINES="RELEASE") print("CXXFLAGS={}, CPPDEFINES={}".format(env['CXXFLAGS'], env['CPPDEFINES'])) # notice including a leading space in CXXFLAGS value env.Append(CXXFLAGS=" -O", CPPDEFINES="EXTRA") print("CXXFLAGS={}, CPPDEFINES={}".format(env['CXXFLAGS'], env['CPPDEFINES'])) print("CPPDEFINES will expand to {}".format(env.subst("$_CPPDEFFLAGS"))) $ scons -Q CXXFLAGS=-std=c11, CPPDEFINES=RELEASE CXXFLAGS=-std=c11 -O, CPPDEFINES=['RELEASE', 'EXTRA'] CPPDEFINES will expand to -DRELEASE -DEXTRA scons: `.' is up to date. Because &cv-link-CPPDEFINES; is intended to describe C/C++ pre-processor macro definitions, it accepts additional syntax. Preprocessor macros can be valued, or un-valued, as in -DBAR=1 or -DFOO. The macro can be be supplied as a complete string including the value, or as a tuple (or list) of macro, value, or as a dictionary. Example (again gcc syntax in the expanded defines): env = Environment(CPPDEFINES="FOO") print("CPPDEFINES={}".format(env['CPPDEFINES'])) env.Append(CPPDEFINES="BAR=1") print("CPPDEFINES={}".format(env['CPPDEFINES'])) env.Append(CPPDEFINES=("OTHER", 2)) print("CPPDEFINES={}".format(env['CPPDEFINES'])) env.Append(CPPDEFINES={"EXTRA": "arg"}) print("CPPDEFINES={}".format(env['CPPDEFINES'])) print("CPPDEFINES will expand to {}".format(env.subst("$_CPPDEFFLAGS"))) $ scons -Q CPPDEFINES=FOO CPPDEFINES=['FOO', 'BAR=1'] CPPDEFINES=['FOO', 'BAR=1', ('OTHER', 2)] CPPDEFINES=['FOO', 'BAR=1', ('OTHER', 2), {'EXTRA': 'arg'}] CPPDEFINES will expand to -DFOO -DBAR=1 -DOTHER=2 -DEXTRA=arg scons: `.' is up to date. Adding a string val to a dictonary &consvar; will enter val as the key in the dict, and None as its value. Using a tuple type to supply a key + value only works for the special case of &cv-link-CPPDEFINES; described above. Although most combinations of types work without needing to know the details, some combinations do not make sense and a Python exception will be raised. When using &f-env-Append; to modify &consvars; which are path specifications (normally, those names which end in PATH), it is recommended to add the values as a list of strings, even if there is only a single string to add. The same goes for adding library names to &cv-LIBS;. env.Append(CPPPATH=["#/include"]) See also &f-link-env-AppendUnique;, &f-link-env-Prepend; and &f-link-env-PrependUnique;.

(name, newpath, [envname, sep, delete_existing=False])

Append new path elements to the given path in the specified external environment (&cv-link-ENV; by default). This will only add any particular path once (leaving the last one it encounters and ignoring the rest, to preserve path order), and to help assure this, will normalize all paths (using os.path.normpath and os.path.normcase). This can also handle the case where the given old path variable is a list instead of a string, in which case a list will be returned instead of a string. If delete_existing is False, then adding a path that already exists will not move it to the end; it will stay where it is in the list. Example: print('before:', env['ENV']['INCLUDE']) include_path = '/foo/bar:/foo' env.AppendENVPath('INCLUDE', include_path) print('after:', env['ENV']['INCLUDE']) Yields: before: /foo:/biz after: /biz:/foo/bar:/foo

(key=val, [...], delete_existing=False)

Append values to &consvars; in the current &consenv;, maintaining uniqueness. Works like &f-link-env-Append; (see for details), except that values already present in the &consvar; will not be added again. If delete_existing is True, the existing matching value is first removed, and the requested value is added, having the effect of moving such values to the end. Example: env.AppendUnique(CCFLAGS='-g', FOO=['foo.yyy']) See also &f-link-env-Append;, &f-link-env-Prepend; and &f-link-env-PrependUnique;.

(action, [arguments])

Creates a Builder object for the specified action. See the manpage section "Builder Objects" for a complete explanation of the arguments and behavior. Note that the env.Builder() form of the invocation will expand construction variables in any arguments strings, including the action argument, at the time it is called using the construction variables in the env construction environment through which &f-env-Builder; was called. The &f-Builder; form delays all variable expansion until after the Builder object is actually called.

(cache_dir)

Direct &scons; to maintain a derived-file cache in cache_dir. The derived files in the cache will be shared among all the builds specifying the same cache_dir. Specifying a cache_dir of None disables derived file caching. Calling the environment method &f-link-env-CacheDir; limits the effect to targets built through the specified construction environment. Calling the global function &f-link-CacheDir; sets a global default that will be used by all targets built through construction environments that do not set up environment-specific caching by calling &f-env-CacheDir;. When derived-file caching is being used and &scons; finds a derived file that needs to be rebuilt, it will first look in the cache to see if a file with matching build signature exists (indicating the input file(s) and build action(s) were identical to those for the current target), and if so, will retrieve the file from the cache. &scons; will report Retrieved `file' from cache instead of the normal build message. If the derived file is not present in the cache, &scons; will build it and then place a copy of the built file in the cache, identified by its build signature, for future use. The Retrieved `file' from cache messages are useful for human consumption, but less so when comparing log files between &scons; runs which will show differences that are noisy and not actually significant. To disable, use the --cache-show option. With this option, &scons; will print the action that would have been used to build the file without considering cache retrieval. Derived-file caching may be disabled for any invocation of &scons; by giving the --cache-disable command line option. Cache updating may be disabled, leaving cache fetching enabled, by giving the --cache-readonly. If the --cache-force option is used, &scons; will place a copy of all derived files in the cache, even if they already existed and were not built by this invocation. This is useful to populate a cache the first time a cache_dir is used for a build, or to bring a cache up to date after a build with cache updating disabled (--cache-disable or --cache-readonly) has been done. The &f-link-NoCache; method can be used to disable caching of specific files. This can be useful if inputs and/or outputs of some tool are impossible to predict or prohibitively large.

(targets, files_or_dirs)

This specifies a list of files or directories which should be removed whenever the targets are specified with the -c command line option. The specified targets may be a list or an individual target. Multiple calls to &f-Clean; are legal, and create new targets or add files and directories to the clean list for the specified targets. Multiple files or directories should be specified either as separate arguments to the &f-Clean; method, or as a list. &f-Clean; will also accept the return value of any of the construction environment Builder methods. Examples: The related &f-link-NoClean; function overrides calling &f-Clean; for the same target, and any targets passed to both functions will not be removed by the -c option. Examples: Clean('foo', ['bar', 'baz']) Clean('dist', env.Program('hello', 'hello.c')) Clean(['foo', 'bar'], 'something_else_to_clean') In this example, installing the project creates a subdirectory for the documentation. This statement causes the subdirectory to be removed if the project is deinstalled. Clean(docdir, os.path.join(docdir, projectname))

([key=val, ...])

Returns a separate copy of a construction environment. If there are any keyword arguments specified, they are added to the returned copy, overwriting any existing values for the keywords. Example: env2 = env.Clone() env3 = env.Clone(CCFLAGS='-g') Additionally, a list of tools and a toolpath may be specified, as in the &f-link-Environment; constructor: def MyTool(env): env['FOO'] = 'bar' env4 = env.Clone(tools=['msvc', MyTool]) The parse_flags keyword argument is also recognized to allow merging command-line style arguments into the appropriate construction variables (see &f-link-env-MergeFlags;). # create an environment for compiling programs that use wxWidgets wx_env = env.Clone(parse_flags='!wx-config --cflags --cxxflags')

The &b-Command; "Builder" is actually a function that looks like a Builder, but takes a required third argument, which is the action to take to construct the target from the source, used for "one-off" builds where a full builder is not needed. Thus it does not follow the builder calling rules described at the start of this section. See instead the &f-link-Command; function description for the calling syntax and details.

(target, source, action, [key=val, ...])

Executes a specific action (or list of actions) to build a target file or files from a source file or files. This is more convenient than defining a separate Builder object for a single special-case build. The &Command; function accepts source_scanner, target_scanner, source_factory, and target_factory keyword arguments. These arguments can be used to specify a Scanner object that will be used to apply a custom scanner for a source or target. For example, the global DirScanner object can be used if any of the sources will be directories that must be scanned on-disk for changes to files that aren't already specified in other Builder of function calls. The *_factory arguments take a factory function that &Command; will use to turn any sources or targets specified as strings into SCons Nodes. See the manpage section "Builder Objects" for more information about how these arguments work in a Builder. Any other keyword arguments specified override any same-named existing construction variables. An action can be an external command, specified as a string, or a callable Python object; see the manpage section "Action Objects" for more complete information. Also note that a string specifying an external command may be preceded by an at-sign (@) to suppress printing the command in question, or by a hyphen (-) to ignore the exit status of the external command. Examples: env.Command( target='foo.out', source='foo.in', action="$FOO_BUILD < $SOURCES > $TARGET" ) env.Command( target='bar.out', source='bar.in', action=["rm -f $TARGET", "$BAR_BUILD < $SOURCES > $TARGET"], ENV={'PATH': '/usr/local/bin/'}, ) import os def rename(env, target, source): os.rename('.tmp', str(target[0])) env.Command( target='baz.out', source='baz.in', action=["$BAZ_BUILD < $SOURCES > .tmp", rename], ) Note that the &Command; function will usually assume, by default, that the specified targets and/or sources are Files, if no other part of the configuration identifies what type of entries they are. If necessary, you can explicitly specify that targets or source nodes should be treated as directories by using the &f-link-Dir; or &f-link-env-Dir; functions. Examples: env.Command('ddd.list', Dir('ddd'), 'ls -l $SOURCE > $TARGET') env['DISTDIR'] = 'destination/directory' env.Command(env.Dir('$DISTDIR')), None, make_distdir) Also note that SCons will usually automatically create any directory necessary to hold a target file, so you normally don't need to create directories by hand.

(env, [custom_tests, conf_dir, log_file, config_h]) ([custom_tests, conf_dir, log_file, config_h])

Creates a Configure object for integrated functionality similar to GNU autoconf. See the manpage section "Configure Contexts" for a complete explanation of the arguments and behavior.

(function)

Specifies that all up-to-date decisions for targets built through this construction environment will be handled by the specified function. function can be the name of a function or one of the following strings that specify the predefined decision function that will be applied: "timestamp-newer" Specifies that a target shall be considered out of date and rebuilt if the dependency's timestamp is newer than the target file's timestamp. This is the behavior of the classic Make utility, and make can be used a synonym for timestamp-newer. "timestamp-match" Specifies that a target shall be considered out of date and rebuilt if the dependency's timestamp is different than the timestamp recorded the last time the target was built. This provides behavior very similar to the classic Make utility (in particular, files are not opened up so that their contents can be checksummed) except that the target will also be rebuilt if a dependency file has been restored to a version with an earlier timestamp, such as can happen when restoring files from backup archives. "content" Specifies that a target shall be considered out of date and rebuilt if the dependency's content has changed since the last time the target was built, as determined be performing an checksum on the dependency's contents and comparing it to the checksum recorded the last time the target was built. MD5 can be used as a synonym for content, but it is deprecated. "content-timestamp" Specifies that a target shall be considered out of date and rebuilt if the dependency's content has changed since the last time the target was built, except that dependencies with a timestamp that matches the last time the target was rebuilt will be assumed to be up-to-date and not rebuilt. This provides behavior very similar to the content behavior of always checksumming file contents, with an optimization of not checking the contents of files whose timestamps haven't changed. The drawback is that SCons will not detect if a file's content has changed but its timestamp is the same, as might happen in an automated script that runs a build, updates a file, and runs the build again, all within a single second. MD5-timestamp can be used as a synonym for content-timestamp, but it is deprecated. Examples: # Use exact timestamp matches by default. Decider('timestamp-match') # Use hash content signatures for any targets built # with the attached construction environment. env.Decider('content') In addition to the above already-available functions, the function argument may be a Python function you supply. Such a function must accept the following four arguments: dependency The Node (file) which should cause the target to be rebuilt if it has "changed" since the last tme target was built. target The Node (file) being built. In the normal case, this is what should get rebuilt if the dependency has "changed." prev_ni Stored information about the state of the dependency the last time the target was built. This can be consulted to match various file characteristics such as the timestamp, size, or content signature. repo_node If set, use this Node instead of the one specified by dependency to determine if the dependency has changed. This argument is optional so should be written as a default argument (typically it would be written as repo_node=None). A caller will normally only set this if the target only exists in a Repository. The function should return a value which evaluates True if the dependency has "changed" since the last time the target was built (indicating that the target should be rebuilt), and a value which evaluates False otherwise (indicating that the target should not be rebuilt). Note that the decision can be made using whatever criteria are appopriate. Ignoring some or all of the function arguments is perfectly normal. Example: def my_decider(dependency, target, prev_ni, repo_node=None): return not os.path.exists(str(target)) env.Decider(my_decider)

(target, dependency)

Specifies an explicit dependency; the target will be rebuilt whenever the dependency has changed. Both the specified target and dependency can be a string (usually the path name of a file or directory) or Node objects, or a list of strings or Node objects (such as returned by a Builder call). This should only be necessary for cases where the dependency is not caught by a Scanner for the file. Example: env.Depends('foo', 'other-input-file-for-foo') mylib = env.Library('mylib.c') installed_lib = env.Install('lib', mylib) bar = env.Program('bar.c') # Arrange for the library to be copied into the installation # directory before trying to build the "bar" program. # (Note that this is for example only. A "real" library # dependency would normally be configured through the $LIBS # and $LIBPATH variables, not using an env.Depends() call.) env.Depends(bar, installed_lib)

(progs)

Find an executable from one or more choices: progs may be a string or a list of strings. Returns the first value from progs that was found, or None. Executable is searched by checking the paths specified by env['ENV']['PATH']. On Windows systems, additionally applies the filename suffixes found in env['ENV']['PATHEXT'] but will not include any such extension in the return value. &f-env-Detect; is a wrapper around &f-link-env-WhereIs;.

([vars])

Returns a dictionary object containing the &consvars; in the &consenv;. If there are any arguments specified, the values of the specified &consvars; are returned as a string (if one argument) or as a list of strings. Example: cvars = env.Dictionary() cc_values = env.Dictionary('CC', 'CCFLAGS', 'CCCOM')

(name, [directory])

Returns Directory Node(s). A Directory Node is an object that represents a directory. name can be a relative or absolute path or a list of such paths. directory is an optional directory that will be used as the parent directory. If no directory is specified, the current script's directory is used as the parent. If name is a single pathname, the corresponding node is returned. If name is a list, SCons returns a list of nodes. Construction variables are expanded in name. Directory Nodes can be used anywhere you would supply a string as a directory name to a Builder method or function. Directory Nodes have attributes and methods that are useful in many situations; see manpage section "File and Directory Nodes" for more information.

([key], [format])

Serializes &consvars; to a string. The method supports the following formats specified by format: pretty Returns a pretty printed representation of the environment (if format is not specified, this is the default). json Returns a JSON-formatted string representation of the environment. If key is None (the default) the entire dictionary of &consvars; is serialized. If supplied, it is taken as the name of a &consvar; whose value is serialized. This SConstruct: env=Environment() print(env.Dump('CCCOM')) will print: '$CC -c -o $TARGET $CCFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS $SOURCES' While this SConstruct: env = Environment() print(env.Dump()) will print: { 'AR': 'ar', 'ARCOM': '$AR $ARFLAGS $TARGET $SOURCES\n$RANLIB $RANLIBFLAGS $TARGET', 'ARFLAGS': ['r'], 'AS': 'as', 'ASCOM': '$AS $ASFLAGS -o $TARGET $SOURCES', 'ASFLAGS': [], ...

([key=value, ...])

Return a new construction environment initialized with the specified key=value pairs. The keyword arguments parse_flags, platform, toolpath, tools and variables are also specially recognized. See the manpage section "Construction Environments" for more details.

(action, [strfunction, varlist])

Executes an Action object. The specified action may be an Action object (see manpage section "Action Objects" for an explanation of behavior), or it may be a command-line string, list of commands, or executable Python function, each of which will be converted into an Action object and then executed. Any additional arguments to &f-Execute; (strfunction, varlist) are passed on to the &f-link-Action; factory function which actually creates the Action object. The exit value of the command or return value of the Python function will be returned. Note that &scons; will print an error message if the executed action fails--that is, exits with or returns a non-zero value. &scons; will not, however, automatically terminate the build if the specified action fails. If you want the build to stop in response to a failed &f-Execute; call, you must explicitly check for a non-zero return value: Execute(Copy('file.out', 'file.in')) if Execute("mkdir sub/dir/ectory"): # The mkdir failed, don't try to build. Exit(1)

(name, [directory])

Returns File Node(s). A File Node is an object that represents a file. name can be a relative or absolute path or a list of such paths. directory is an optional directory that will be used as the parent directory. If no directory is specified, the current script's directory is used as the parent. If name is a single pathname, the corresponding node is returned. If name is a list, SCons returns a list of nodes. Construction variables are expanded in name. File Nodes can be used anywhere you would supply a string as a file name to a Builder method or function. File Nodes have attributes and methods that are useful in many situations; see manpage section "File and Directory Nodes" for more information.

(file, dirs)

Search for file in the path specified by dirs. dirs may be a list of directory names or a single directory name. In addition to searching for files that exist in the filesystem, this function also searches for derived files that have not yet been built. Example: foo = env.FindFile('foo', ['dir1', 'dir2'])

()

Returns the list of targets set up by the &b-link-Install; or &b-link-InstallAs; builders. This function serves as a convenient method to select the contents of a binary package. Example: Install('/bin', ['executable_a', 'executable_b']) # will return the file node list # ['/bin/executable_a', '/bin/executable_b'] FindInstalledFiles() Install('/lib', ['some_library']) # will return the file node list # ['/bin/executable_a', '/bin/executable_b', '/lib/some_library'] FindInstalledFiles()

(node='"."')

Returns the list of nodes which serve as the source of the built files. It does so by inspecting the dependency tree starting at the optional argument node which defaults to the '"."'-node. It will then return all leaves of node. These are all children which have no further children. This function is a convenient method to select the contents of a Source Package. Example: Program('src/main_a.c') Program('src/main_b.c') Program('main_c.c') # returns ['main_c.c', 'src/main_a.c', 'SConstruct', 'src/main_b.c'] FindSourceFiles() # returns ['src/main_b.c', 'src/main_a.c' ] FindSourceFiles('src') As you can see build support files (SConstruct in the above example) will also be returned by this function.

(sequence)

Takes a sequence (that is, a Python list or tuple) that may contain nested sequences and returns a flattened list containing all of the individual elements in any sequence. This can be helpful for collecting the lists returned by calls to Builders; other Builders will automatically flatten lists specified as input, but direct Python manipulation of these lists does not. Examples: foo = Object('foo.c') bar = Object('bar.c') # Because `foo' and `bar' are lists returned by the Object() Builder, # `objects' will be a list containing nested lists: objects = ['f1.o', foo, 'f2.o', bar, 'f3.o'] # Passing such a list to another Builder is all right because # the Builder will flatten the list automatically: Program(source = objects) # If you need to manipulate the list directly using Python, you need to # call Flatten() yourself, or otherwise handle nested lists: for object in Flatten(objects): print(str(object))

(file, [...])

Returns the &scons; path name (or names) for the specified file (or files). The specified file or files may be &scons; Nodes or strings representing path names.

(pattern, [ondisk, source, strings, exclude])

Returns Nodes (or strings) that match the specified pattern, relative to the directory of the current &SConscript; file. The evironment method form (&f-env-Glob;) performs string substition on pattern and returns whatever matches the resulting expanded pattern. The specified pattern uses Unix shell style metacharacters for matching: * matches everything ? matches any single character [seq] matches any character in seq [!seq] matches any char not in seq If the first character of a filename is a dot, it must be matched explicitly. Character matches do not span directory separators. The &f-Glob; knows about repositories (see the &f-link-Repository; function) and source directories (see the &f-link-VariantDir; function) and returns a Node (or string, if so configured) in the local (SConscript) directory if a matching Node is found anywhere in a corresponding repository or source directory. The ondisk argument may be set to a value which evaluates False to disable the search for matches on disk, thereby only returning matches among already-configured File or Dir Nodes. The default behavior is to return corresponding Nodes for any on-disk matches found. The source argument may be set to a value which evaluates True to specify that, when the local directory is a &f-VariantDir;, the returned Nodes should be from the corresponding source directory, not the local directory. The strings argument may be set to a value which evaluates True to have the &f-Glob; function return strings, not Nodes, that represent the matched files or directories. The returned strings will be relative to the local (SConscript) directory. (Note that This may make it easier to perform arbitrary manipulation of file names, but if the returned strings are passed to a different &SConscript; file, any Node translation will be relative to the other &SConscript; directory, not the original &SConscript; directory.) The exclude argument may be set to a pattern or a list of patterns (following the same Unix shell semantics) which must be filtered out of returned elements. Elements matching a least one pattern of this list will be excluded. Examples: Program("foo", Glob("*.c")) Zip("/tmp/everything", Glob(".??*") + Glob("*")) sources = Glob("*.cpp", exclude=["os_*_specific_*.cpp"]) + \ Glob( "os_%s_specific_*.cpp" % currentOS)

(target, dependency)

The specified dependency file(s) will be ignored when deciding if the target file(s) need to be rebuilt. You can also use &f-Ignore; to remove a target from the default build. In order to do this you must specify the directory the target will be built in as the target, and the file you want to skip building as the dependency. Note that this will only remove the dependencies listed from the files built by default. It will still be built if that dependency is needed by another object being built. See the third and forth examples below. Examples: env.Ignore('foo', 'foo.c') env.Ignore('bar', ['bar1.h', 'bar2.h']) env.Ignore('.', 'foobar.obj') env.Ignore('bar', 'bar/foobar.obj')

(string)

The specified string will be preserved as-is and not have construction variables expanded.

(targets)

The specified targets will have copies made in the local tree, even if an already up-to-date copy exists in a repository. Returns a list of the target Node or Nodes.

(arg, [unique])

Merges the specified arg values to the construction environment's construction variables. If the arg argument is not a dictionary, it is converted to one by calling &f-link-env-ParseFlags; on the argument before the values are merged. Note that arg must be a single value, so multiple strings must be passed in as a list, not as separate arguments to &f-env-MergeFlags;. By default, duplicate values are eliminated; you can, however, specify unique=0 to allow duplicate values to be added. When eliminating duplicate values, any construction variables that end with the string PATH keep the left-most unique value. All other construction variables keep the right-most unique value. Examples: # Add an optimization flag to $CCFLAGS. env.MergeFlags('-O3') # Combine the flags returned from running pkg-config with an optimization # flag and merge the result into the construction variables. env.MergeFlags(['!pkg-config gtk+-2.0 --cflags', '-O3']) # Combine an optimization flag with the flags returned from running pkg-config # twice and merge the result into the construction variables. env.MergeFlags(['-O3', '!pkg-config gtk+-2.0 --cflags --libs', '!pkg-config libpng12 --cflags --libs'])

(target, ...)

Specifies a list of files which should not be cached whenever the &f-link-CacheDir; method has been activated. The specified targets may be a list or an individual target. Multiple files should be specified either as separate arguments to the &f-NoCache; method, or as a list. &f-NoCache; will also accept the return value of any of the construction environment Builder methods. Calling &f-NoCache; on directories and other non-File Node types has no effect because only File Nodes are cached. Examples: NoCache('foo.elf') NoCache(env.Program('hello', 'hello.c'))

(target, ...)

Specifies a list of files or directories which should not be removed whenever the targets (or their dependencies) are specified with the -c command line option. The specified targets may be a list or an individual target. Multiple calls to &f-NoClean; are legal, and prevent each specified target from being removed by calls to the -c option. Multiple files or directories should be specified either as separate arguments to the &f-NoClean; method, or as a list. &f-NoClean; will also accept the return value of any of the construction environment Builder methods. Calling &f-NoClean; for a target overrides calling &f-link-Clean; for the same target, and any targets passed to both functions will not be removed by the -c option. Examples: NoClean('foo.elf') NoClean(env.Program('hello', 'hello.c'))

(command, [function, unique])

Calls the specified function to modify the environment as specified by the output of command. The default function is &f-link-env-MergeFlags;, which expects the output of a typical *-config command (for example, gtk-config) and adds the options to the appropriate construction variables. By default, duplicate values are not added to any construction variables; you can specify unique=0 to allow duplicate values to be added. Interpreted options and the construction variables they affect are as specified for the &f-link-env-ParseFlags; method (which this method calls). See that method's description for a table of options and construction variables.

(filename, [must_exist, only_one])

Parses the contents of the specified filename as a list of dependencies in the style of &Make; or mkdep, and explicitly establishes all of the listed dependencies. By default, it is not an error if the specified filename does not exist. The optional must_exist argument may be set to a non-zero value to have scons throw an exception and generate an error if the file does not exist, or is otherwise inaccessible. The optional only_one argument may be set to a non-zero value to have scons thrown an exception and generate an error if the file contains dependency information for more than one target. This can provide a small sanity check for files intended to be generated by, for example, the gcc -M flag, which should typically only write dependency information for one output file into a corresponding .d file. The filename and all of the files listed therein will be interpreted relative to the directory of the &SConscript; file which calls the &f-ParseDepends; function.

(flags, ...)

Parses one or more strings containing typical command-line flags for GCC tool chains and returns a dictionary with the flag values separated into the appropriate SCons construction variables. This is intended as a companion to the &f-link-env-MergeFlags; method, but allows for the values in the returned dictionary to be modified, if necessary, before merging them into the construction environment. (Note that &f-env-MergeFlags; will call this method if its argument is not a dictionary, so it is usually not necessary to call &f-link-env-ParseFlags; directly unless you want to manipulate the values.) If the first character in any string is an exclamation mark (!), the rest of the string is executed as a command, and the output from the command is parsed as GCC tool chain command-line flags and added to the resulting dictionary. Flag values are translated accordig to the prefix found, and added to the following construction variables: -arch CCFLAGS, LINKFLAGS -D CPPDEFINES -framework FRAMEWORKS -frameworkdir= FRAMEWORKPATH -fmerge-all-constants CCFLAGS, LINKFLAGS -fopenmp CCFLAGS, LINKFLAGS -include CCFLAGS -imacros CCFLAGS -isysroot CCFLAGS, LINKFLAGS -isystem CCFLAGS -iquote CCFLAGS -idirafter CCFLAGS -I CPPPATH -l LIBS -L LIBPATH -mno-cygwin CCFLAGS, LINKFLAGS -mwindows LINKFLAGS -openmp CCFLAGS, LINKFLAGS -pthread CCFLAGS, LINKFLAGS -std= CFLAGS -Wa, ASFLAGS, CCFLAGS -Wl,-rpath= RPATH -Wl,-R, RPATH -Wl,-R RPATH -Wl, LINKFLAGS -Wp, CPPFLAGS - CCFLAGS + CCFLAGS, LINKFLAGS Any other strings not associated with options are assumed to be the names of libraries and added to the &cv-LIBS; construction variable. Examples (all of which produce the same result): dict = env.ParseFlags('-O2 -Dfoo -Dbar=1') dict = env.ParseFlags('-O2', '-Dfoo', '-Dbar=1') dict = env.ParseFlags(['-O2', '-Dfoo -Dbar=1']) dict = env.ParseFlags('-O2', '!echo -Dfoo -Dbar=1')

(string)

The &f-Platform; form returns a callable object that can be used to initialize a construction environment using the platform keyword of the &f-Environment; function. Example: env = Environment(platform=Platform('win32')) The &f-env-Platform; form applies the callable object for the specified platform string to the environment through which the method was called. env.Platform('posix') Note that the win32 platform adds the SystemDrive and SystemRoot variables from the user's external environment to the construction environment's &cv-link-ENV; dictionary. This is so that any executed commands that use sockets to connect with other systems (such as fetching source files from external CVS repository specifications like :pserver:anonymous@cvs.sourceforge.net:/cvsroot/scons) will work on Windows systems.

(key=val, [...])

Prepend values to &consvars; in the current &consenv;, Works like &f-link-env-Append; (see for details), except that values are added to the front, rather than the end, of any existing value of the &consvar; Example: env.Prepend(CCFLAGS='-g ', FOO=['foo.yyy']) See also &f-link-env-Append;, &f-link-env-AppendUnique; and &f-link-env-PrependUnique;.

(name, newpath, [envname, sep, delete_existing])

Prepend new path elements to the given path in the specified external environment (&cv-link-ENV; by default). This will only add any particular path once (leaving the first one it encounters and ignoring the rest, to preserve path order), and to help assure this, will normalize all paths (using os.path.normpath and os.path.normcase). This can also handle the case where the given old path variable is a list instead of a string, in which case a list will be returned instead of a string. If delete_existing is False, then adding a path that already exists will not move it to the beginning; it will stay where it is in the list. Example: print('before:', env['ENV']['INCLUDE']) include_path = '/foo/bar:/foo' env.PrependENVPath('INCLUDE', include_path) print('after:', env['ENV']['INCLUDE']) Yields: before: /biz:/foo after: /foo/bar:/foo:/biz

(key=val, delete_existing=False, [...])

Prepend values to &consvars; in the current &consenv;, maintaining uniqueness. Works like &f-link-env-Append; (see for details), except that values are added to the front, rather than the end, of any existing value of the the &consvar;, and values already present in the &consvar; will not be added again. If delete_existing is True, the existing matching value is first removed, and the requested value is inserted, having the effect of moving such values to the front. Example: env.PrependUnique(CCFLAGS='-g', FOO=['foo.yyy']) See also &f-link-env-Append;, &f-link-env-AppendUnique; and &f-link-env-Prepend;.

(modulename)

This returns a Directory Node similar to Dir. The python module / package is looked up and if located the directory is returned for the location. modulename Is a named python package / module to lookup the directory for it's location. If modulename is a list, SCons returns a list of Dir nodes. Construction variables are expanded in modulename.

(key=val, [...])

Replaces construction variables in the Environment with the specified keyword arguments. Example: env.Replace(CCFLAGS='-g', FOO='foo.xxx')

(directory)

Specifies that directory is a repository to be searched for files. Multiple calls to &f-Repository; are legal, and each one adds to the list of repositories that will be searched. To &scons;, a repository is a copy of the source tree, from the top-level directory on down, which may contain both source files and derived files that can be used to build targets in the local source tree. The canonical example would be an official source tree maintained by an integrator. If the repository contains derived files, then the derived files should have been built using &scons;, so that the repository contains the necessary signature information to allow &scons; to figure out when it is appropriate to use the repository copy of a derived file, instead of building one locally. Note that if an up-to-date derived file already exists in a repository, &scons; will not make a copy in the local directory tree. In order to guarantee that a local copy will be made, use the &f-link-Local; method.

(target, prerequisite)

Specifies an order-only relationship between the specified target file(s) and the specified prerequisite file(s). The prerequisite file(s) will be (re)built, if necessary, before the target file(s), but the target file(s) do not actually depend on the prerequisites and will not be rebuilt simply because the prerequisite file(s) change. Example: env.Requires('foo', 'file-that-must-be-built-before-foo')

(function, [name, argument, skeys, path_function, node_class, node_factory, scan_check, recursive])

Creates a Scanner object for the specified function. See manpage section "Scanner Objects" for a complete explanation of the arguments and behavior.

(value)

By default, &scons; changes its working directory to the directory in which each subsidiary SConscript file lives. This behavior may be disabled by specifying either: SConscriptChdir(0) env.SConscriptChdir(0) in which case &scons; will stay in the top-level directory while reading all SConscript files. (This may be necessary when building from repositories, when all the directories in which SConscript files may be found don't necessarily exist locally.) You may enable and disable this ability by calling SConscriptChdir() multiple times. Example: env = Environment() SConscriptChdir(0) SConscript('foo/SConscript') # will not chdir to foo env.SConscriptChdir(1) SConscript('bar/SConscript') # will chdir to bar

([name, dbm_module])

Specify where to store the &SCons; file signature database, and which database format to use. This may be useful to specify alternate database files and/or file locations for different types of builds. The optional name argument is the base name of the database file(s). If not an absolute path name, these are placed relative to the directory containing the top-level &SConstruct; file. The default is .sconsign. The actual database file(s) stored on disk may have an appropriate suffix appended by the chosen dbm_module The optional dbm_module argument specifies which Python database module to use for reading/writing the file. The module must be imported first; then the imported module name is passed as the argument. The default is a custom SCons.dblite module that uses pickled Python data structures, which works on all Python versions. See documentation of the Python dbm module for other available types. If called with no arguments, the database will default to .sconsign.dblite in the top directory of the project, which is also the default if if &f-SConsignFile; is not called. The setting is global, so the only difference between the global function and the environment method form is variable expansion on name. There should only be one active call to this function/method in a given build setup. If name is set to None, &scons; will store file signatures in a separate .sconsign file in each directory, not in a single combined database file. This is a backwards-compatibility meaure to support what was the default behavior prior to &SCons; 0.97 (i.e. before 2008). Use of this mode is discouraged and may be deprecated in a future &SCons; release. Examples: # Explicitly stores signatures in ".sconsign.dblite" # in the top-level SConstruct directory (the default behavior). SConsignFile() # Stores signatures in the file "etc/scons-signatures" # relative to the top-level SConstruct directory. # SCons will add a database suffix to this name. SConsignFile("etc/scons-signatures") # Stores signatures in the specified absolute file name. # SCons will add a database suffix to this name. SConsignFile("/home/me/SCons/signatures") # Stores signatures in a separate .sconsign file # in each directory. SConsignFile(None) # Stores signatures in a GNU dbm format .sconsign file import dbm.gnu SConsignFile(dbm_module=dbm.gnu)

(key=val, [...])

Sets construction variables to default values specified with the keyword arguments if (and only if) the variables are not already set. The following statements are equivalent: env.SetDefault(FOO='foo') if 'FOO' not in env: env['FOO'] = 'foo'

(side_effect, target)

Declares side_effect as a side effect of building target. Both side_effect and target can be a list, a file name, or a node. A side effect is a target file that is created or updated as a side effect of building other targets. For example, a Windows PDB file is created as a side effect of building the .obj files for a static library, and various log files are created updated as side effects of various TeX commands. If a target is a side effect of multiple build commands, &scons; will ensure that only one set of commands is executed at a time. Consequently, you only need to use this method for side-effect targets that are built as a result of multiple build commands. Because multiple build commands may update the same side effect file, by default the side_effect target is not automatically removed when the target is removed by the -c option. (Note, however, that the side_effect might be removed as part of cleaning the directory in which it lives.) If you want to make sure the side_effect is cleaned whenever a specific target is cleaned, you must specify this explicitly with the &f-link-Clean; or &f-env-Clean; function. This function returns the list of side effect Node objects that were successfully added. If the list of side effects contained any side effects that had already been added, they are not added and included in the returned list.

(arg)

Returns a list of file names or other objects. If arg is a string, it will be split on strings of white-space characters within the string, making it easier to write long lists of file names. If arg is already a list, the list will be returned untouched. If arg is any other type of object, it will be returned as a list containing just the object. Example: files = Split("f1.c f2.c f3.c") files = env.Split("f4.c f5.c f6.c") files = Split(""" f7.c f8.c f9.c """)

(input, [raw, target, source, conv])

Performs construction variable interpolation on the specified string or sequence argument input. By default, leading or trailing white space will be removed from the result. and all sequences of white space will be compressed to a single space character. Additionally, any $( and $) character sequences will be stripped from the returned string, The optional raw argument may be set to 1 if you want to preserve white space and $(-$) sequences. The raw argument may be set to 2 if you want to strip all characters between any $( and $) pairs (as is done for signature calculation). If the input is a sequence (list or tuple), the individual elements of the sequence will be expanded, and the results will be returned as a list. The optional target and source keyword arguments must be set to lists of target and source nodes, respectively, if you want the &cv-TARGET;, &cv-TARGETS;, &cv-SOURCE; and &cv-SOURCES; to be available for expansion. This is usually necessary if you are calling &f-env-subst; from within a Python function used as an SCons action. Returned string values or sequence elements are converted to their string representation by default. The optional conv argument may specify a conversion function that will be used in place of the default. For example, if you want Python objects (including SCons Nodes) to be returned as Python objects, you can use the Python λ idiom to pass in an unnamed function that simply returns its unconverted argument. Example: print(env.subst("The C compiler is: $CC")) def compile(target, source, env): sourceDir = env.subst( "${SOURCE.srcdir}", target=target, source=source ) source_nodes = env.subst('$EXPAND_TO_NODELIST', conv=lambda x: x)

(name, [toolpath, **kwargs])

Runs the tool identified by name, which is searched for in standard locations and any paths specified by the optional toolpath, to update a &consenv; with &consvars; needed to use the mechanisms that tool describes. Any additional keyword arguments kwargs are passed on to the tool module's generate function. When called as a &consenv; method, the tool module is called to update the &consenv; and the name of the tool is appended to the &cv-link-TOOLS; &consvar; in that environment. Examples: env.Tool('gcc') env.Tool('opengl', toolpath=['build/tools']) When called as a global function, returns a callable tool object; the tool is not called at this time, as it lacks the context of an environment to update. This tool object can be passed to an &f-link-Environment; or &f-link-Clone; call as part of the tools keyword argument, or it can be called directly, passing a &consenv; to update as the argument. Either approach will also update the &cv-TOOLS; &consvar;. Examples: env = Environment(tools=[Tool('msvc')]) env = Environment() t = Tool('msvc') t(env) # adds 'msvc' to the TOOLS variable u = Tool('opengl', toolpath = ['tools']) u(env) # adds 'opengl' to the TOOLS variable

(value, [built_value], [name])

Returns a Node object representing the specified Python value. Value Nodes can be used as dependencies of targets. If the result of calling str(value) changes between SCons runs, any targets depending on Value(value) will be rebuilt. (This is true even when using timestamps to decide if files are up-to-date.) When using timestamp source signatures, Value Nodes' timestamps are equal to the system time when the Node is created. name can be provided as an alternative name for the resulting Value node; this is advised if the value parameter can't be converted to a string. The returned Value Node object has a write() method that can be used to "build" a Value Node by setting a new value. The optional built_value argument can be specified when the Value Node is created to indicate the Node should already be considered "built." There is a corresponding read() method that will return the built value of the Node. Examples: env = Environment() def create(target, source, env): # A function that will write a 'prefix=$SOURCE' # string into the file name specified as the # $TARGET. with open(str(target[0]), 'wb') as f: f.write('prefix=' + source[0].get_contents()) # Fetch the prefix= argument, if any, from the command # line, and use /usr/local as the default. prefix = ARGUMENTS.get('prefix', '/usr/local') # Attach a .Config() builder for the above function action # to the construction environment. env['BUILDERS']['Config'] = Builder(action = create) env.Config(target = 'package-config', source = Value(prefix)) def build_value(target, source, env): # A function that "builds" a Python Value by updating # the the Python value with the contents of the file # specified as the source of the Builder call ($SOURCE). target[0].write(source[0].get_contents()) output = env.Value('before') input = env.Value('after') # Attach a .UpdateValue() builder for the above function # action to the construction environment. env['BUILDERS']['UpdateValue'] = Builder(action = build_value) env.UpdateValue(target = Value(output), source = Value(input))

(variant_dir, src_dir, [duplicate])

Sets up an alternate build location. When building in the variant_dir, &SCons; backfills as needed with files from src_dir to create a complete build directory. &f-VariantDir; can be called multiple times with the same src_dir to set up multiple builds with different options (variants). The variant location must be in or underneath the project top directory, and src_dir may not be underneath variant_dir. By default, &SCons; physically duplicates the source files and SConscript files as needed into the variant tree. Thus, a build performed in the variant tree is guaranteed to be identical to a build performed in the source tree even if intermediate source files are generated during the build, or if preprocessors or other scanners search for included files relative to the source file, or if individual compilers or other invoked tools are hard-coded to put derived files in the same directory as source files. Only the files &SCons; calculates are needed for the build are duplicated into variant_dir. If possible on the platform, the duplication is performed by linking rather than copying. This behavior is affected by the --duplicate command-line option. Duplicating the source files may be disabled by setting the duplicate argument to False. This will cause &SCons; to invoke Builders using the path names of source files in src_dir and the path names of derived files within variant_dir. This is more efficient than duplicate=True, and is safe for most builds; revert to True if it causes problems. &f-VariantDir; works most naturally with used with a subsidiary SConscript file. The subsidiary SConscript file is called as if it were in variant_dir, regardless of the value of duplicate. This is how you tell &scons; which variant of a source tree to build: # run src/SConscript in two variant directories VariantDir('build/variant1', 'src') SConscript('build/variant1/SConscript') VariantDir('build/variant2', 'src') SConscript('build/variant2/SConscript') See also the &f-link-SConscript; function, described above, for another way to specify a variant directory in conjunction with calling a subsidiary SConscript file. Examples: # use names in the build directory, not the source directory VariantDir('build', 'src', duplicate=0) Program('build/prog', 'build/source.c') # this builds both the source and docs in a separate subtree VariantDir('build', '.', duplicate=0) SConscript(dirs=['build/src','build/doc']) # same as previous example, but only uses SConscript SConscript(dirs='src', variant_dir='build/src', duplicate=0) SConscript(dirs='doc', variant_dir='build/doc', duplicate=0)

(program, [path, pathext, reject])

Searches for the specified executable program, returning the full path to the program or None. When called as a &consenv; method, searches the paths in the path keyword argument, or if None (the default) the paths listed in the &consenv; (env['ENV']['PATH']). The external environment's path list (os.environ['PATH']) is used as a fallback if the key env['ENV']['PATH'] does not exist. On Windows systems, searches for executable programs with any of the file extensions listed in the pathext keyword argument, or if None (the default) the pathname extensions listed in the &consenv; (env['ENV']['PATHEXT']). The external environment's pathname extensions list (os.environ['PATHEXT']) is used as a fallback if the key env['ENV']['PATHEXT'] does not exist. When called as a global function, uses the external environment's path os.environ['PATH'] and path extensions os.environ['PATHEXT'], respectively, if path and pathext are None. Will not select any path name or names in the optional reject list.