This appendix contains descriptions of all of the function and construction environment methods in this version of SCons
Action
(action, [output, [var, ...]] [key=value, ...]
), env
.Action
(action, [output, [var, ...]] [key=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 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
env.Action
was called.
The Action
global function
form delays all variable expansion
until the Action object is actually used.
AddMethod
(object, function, [name]
), env
.AddMethod
(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 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 construction environments
subsequently constructed.
When called using the env.AddMethod
form,
the method is added to the specified construction environment only.
Added methods propagate through env.Clone
calls.
More 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')
AddOption
(opt_str, ..., attr=value, ...
)
Adds a local (project-specific) command-line option.
One or more opt_str
values are
the strings representing how the option can be called,
while the keyword arguments define attributes of the option.
For the most part these are the same as for the
OptionParser.add_option
method in the standard Python library module
optparse
,
but with a few additional capabilities noted below.
See the
optparse documentation
for a thorough discussion of its option-processing capabities.
All options added through AddOption
are placed
in a special "Local Options" option group.
In addition to the arguments and values supported by the
optparse
add_option
method, AddOption
allows setting the
nargs
keyword value to
a string '?'
(question mark)
to indicate that the option argument for
that option string may be omitted.
If the option string is present on the
command line but has no matching option
argument, the value of the
const
keyword argument is produced as the value
of the option.
If the option string is omitted from
the command line, the value of the
default
keyword argument is produced, as usual;
if there is no
default
keyword argument in the AddOption
call,
None
is produced.
optparse
recognizes
abbreviations of long option names,
as long as they can be unambiguously resolved.
For example, if
add_option
is called to
define a --devicename
option,
it will recognize --device
,
--dev
and so forth as long as there is no other option
which could also match to the same abbreviation.
Options added via
AddOption
do not support
the automatic recognition of abbreviations.
Instead, to allow specific abbreviations,
include them as synonyms in the AddOption
call itself.
Once a new command-line option has been added with
AddOption
,
the option value may be accessed using
GetOption
or
env.GetOption
.
If the settable=True
argument
was supplied in the AddOption
call,
the value may also be set later using
SetOption
or
env.SetOption
,
if conditions in an
SConscript
file
require overriding any default value.
Note however that a
value specified on the command line will
always
override a value set in an SConscript file.
Changed in 4.8.0: added the
settable
keyword argument
to enable an added option to be settable via SetOption
.
Help text for an option is a combination
of the string supplied in the
help
keyword
argument to AddOption
and information
collected from the other keyword arguments.
Such help is displayed if the
-h
command line option
is used (but not with -H
).
Help for all local options is displayed
under the separate heading
Local Options.
The options are unsorted - they will appear
in the help text in the order in which the
AddOption
calls occur.
Example:
AddOption( '--prefix', dest='prefix', nargs=1, type='string', action='store', metavar='DIR', help='installation prefix', ) env = Environment(PREFIX=GetOption('prefix'))
For that example, the following help text would be produced:
Local Options: --prefix=DIR installation prefix
Help text for local options may be unavailable if
the Help
function has been called,
see the Help
documentation for details.
As an artifact of the internal implementation,
the behavior of options added by AddOption
which take option arguments is undefined
if whitespace
(rather than an =
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 nargs
keyword is used to specify more than one following
option argument (that is, with a value of 2
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.
AddPostAction
(target, action
), env
.AddPostAction
(target, action
)
Arranges for the specified
action
to be performed
after the specified
target
has been built.
action
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.
foo = Program('foo.c') # remove execute permission from binary: AddPostAction(foo, Chmod('$TARGET', "a-x"))
AddPreAction
(target, action
), env
.AddPreAction
(target, action
)
Arranges for the specified
action
to be performed
before the specified
target
is built.
action
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
(alias, [source, [action]]
), env
.Alias
(alias, [source, [action]]
)
Creates an alias target that
can be used as a reference to zero or more other targets,
specified by the optional source
parameter.
Aliases provide a way to give a shorter or more descriptive
name to specific targets,
and to group multiple targets under a single name.
The alias name, or an Alias Node object,
may be used as a dependency of any other target,
including another alias.
alias
and source
may each be a string or Node object,
or a list of strings or Node objects;
if Nodes are used for
alias
they must be Alias nodes.
If source
is omitted,
the alias is created but has no reference;
if selected for building this will result in a
“Nothing to be done.” message.
An empty alias can be used to define the alias
in a visible place in the project;
it can later be appended to in a subsidiary SConscript file
with the actual target(s) to refer to.
The optional
action
parameter specifies an action or list of actions
that will be executed
whenever the any of the alias targets are out-of-date.
Alias
can be called for an existing alias,
which appends the alias
and/or action
arguments
to the existing lists for that alias.
Returns a list of Alias Node objects representing the alias(es), which exist outside of any physical file system. The alias name space is separate from the name space for tangible targets; to avoid confusion do not reuse target names as alias names.
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 $SOURCES")
AllowSubstExceptions
([exception, ...]
)
Specifies the exceptions that will be allowed
when expanding construction variables.
By default,
any construction variable expansions that generate a
NameError
or
IndexError
exception will expand to a
''
(an empty string) and not cause scons to fail.
All exceptions not in the specified list
will generate an error message
and terminate processing.
If
AllowSubstExceptions
is called multiple times,
each call completely overwrites the previous list
of allowed exceptions.
Example:
# Requires that all construction variable names exist. # (You may wish to do this if you want to enforce strictly # that all construction variables must be defined before use.) AllowSubstExceptions() # Also allow a string containing a zero-division expansion # like '${1 / 0}' to evalute to ''. AllowSubstExceptions(IndexError, NameError, ZeroDivisionError)
AlwaysBuild
(target, ...
), env
.AlwaysBuild
(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
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
AlwaysBuild
.
env
.Append
(key=val, [...]
)
Appends value(s) intelligently to construction variables in
env
.
The construction variables and values to add to them are passed as
key=val
pairs (Python keyword arguments).
env.Append
is designed to allow adding values
without having to think about the data type of an existing construction variable.
Regular Python syntax can also be used to manipulate the construction variable,
but for that you may need to know the types involved,
for example pure Python lets you directly "add" two lists of strings,
but adding a string to a list or a list to a string requires
different syntax - things Append
takes care of.
Some pre-defined construction variables do have type expectations
based on how SCons will use them:
for example $CPPDEFINES
is often a string or a list of strings,
but can also be a list of tuples or a dictionary;
while $LIBEMITTER
is expected to be a callable or list of callables,
and $BUILDERS
is expected to be a dictionary.
Consult the documentation for the various construction variables for more details.
The following descriptions apply to both the Append
and Prepend
methods, as well as their
Unique variants,
with the differences being the insertion point of the added values
and whether duplication is allowed.
val
can be almost any type.
If env
does not have a construction variable
named key
,
then key
is simply
stored with a value of val
.
Otherwise, val
is
combinined with the existing value,
possibly converting into an appropriate type
which can hold the expanded contents.
There are a few special cases to be aware of.
Normally, when two strings are combined,
the result is a new string containing their concatenation
(and you are responsible for supplying any needed separation);
however, the contents of $CPPDEFINES
will
will be postprocessed by adding a prefix and/or suffix
to each entry when the command line is produced,
so SCons keeps them separate -
appending a string will result in a separate string entry,
not a combined string.
For $CPPDEFINES
. as well as
$LIBS
, and the various *PATH
variables,
SCons will amend the variable by supplying the compiler-specific
syntax (e.g. prepending a -D
or /D
prefix for $CPPDEFINES
), so you should omit this syntax when
adding values to these variables.
Examples (gcc syntax shown in the expansion of CPPDEFINES
):
env = Environment(CXXFLAGS="-std=c11", CPPDEFINES="RELEASE") print(f"CXXFLAGS = {env['CXXFLAGS']}, CPPDEFINES = {env['CPPDEFINES']}") # notice including a leading space in CXXFLAGS addition env.Append(CXXFLAGS=" -O", CPPDEFINES="EXTRA") print(f"CXXFLAGS = {env['CXXFLAGS']}, CPPDEFINES = {env['CPPDEFINES']}") print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))
$ scons -Q CXXFLAGS = -std=c11, CPPDEFINES = RELEASE CXXFLAGS = -std=c11 -O, CPPDEFINES = deque(['RELEASE', 'EXTRA']) CPPDEFINES will expand to -DRELEASE -DEXTRA scons: `.' is up to date.
Because $CPPDEFINES
is intended for command-line
specification of C/C++ preprocessor macros,
additional syntax is accepted when adding to it.
The preprocessor accepts arguments to predefine a macro name by itself
(-DFOO
for most compilers,
/DFOO
for Microsoft C++),
which gives it an implicit value of 1
,
or can be given with a replacement value
(-DBAR=TEXT
).
SCons follows these rules when adding to $CPPDEFINES
:
A string is split on spaces,
giving an easy way to enter multiple macros in one addition.
Use an =
to specify a valued macro.
A tuple is treated as a valued macro.
Use the value None
if the macro should not have a value.
It is an error to supply more than two elements in such a tuple.
A list is processed in order, adding each item without further interpretation. In this case, space-separated strings are not split.
A dictionary is processed in order,
adding each key-value pair as a valued macro.
Use the value None
if the macro should not have a value.
Examples:
env = Environment(CPPDEFINES="FOO") print("CPPDEFINES =", env['CPPDEFINES']) env.Append(CPPDEFINES="BAR=1") print("CPPDEFINES =", env['CPPDEFINES']) env.Append(CPPDEFINES=[("OTHER", 2)]) print("CPPDEFINES =", env['CPPDEFINES']) env.Append(CPPDEFINES={"EXTRA": "arg"}) print("CPPDEFINES =", env['CPPDEFINES']) print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))
$ scons -Q CPPDEFINES = FOO CPPDEFINES = deque(['FOO', 'BAR=1']) CPPDEFINES = deque(['FOO', 'BAR=1', ('OTHER', 2)]) CPPDEFINES = deque(['FOO', 'BAR=1', ('OTHER', 2), ('EXTRA', 'arg')]) CPPDEFINES will expand to -DFOO -DBAR=1 -DOTHER=2 -DEXTRA=arg scons: `.' is up to date.
Examples of adding multiple macros:
env = Environment() env.Append(CPPDEFINES=[("ONE", 1), "TWO", ("THREE", )]) print("CPPDEFINES =", env['CPPDEFINES']) env.Append(CPPDEFINES={"FOUR": 4, "FIVE": None}) print("CPPDEFINES =", env['CPPDEFINES']) print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))
$ scons -Q CPPDEFINES = [('ONE', 1), 'TWO', ('THREE',)] CPPDEFINES = deque([('ONE', 1), 'TWO', ('THREE',), ('FOUR', 4), ('FIVE', None)]) CPPDEFINES will expand to -DONE=1 -DTWO -DTHREE -DFOUR=4 -DFIVE scons: `.' is up to date.
Changed in version 4.5: clarifined the use of tuples vs. other types, handling is now consistent across the four functions.
env = Environment() env.Append(CPPDEFINES=("MACRO1", "MACRO2")) print("CPPDEFINES =", env['CPPDEFINES']) env.Append(CPPDEFINES=[("MACRO3", "MACRO4")]) print("CPPDEFINES =", env['CPPDEFINES']) print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))
$ scons -Q CPPDEFINES = ('MACRO1', 'MACRO2') CPPDEFINES = deque(['MACRO1', 'MACRO2', ('MACRO3', 'MACRO4')]) CPPDEFINES will expand to -DMACRO1 -DMACRO2 -DMACRO3=MACRO4 scons: `.' is up to date.
See $CPPDEFINES
for more details.
Appending a string val
to a dictonary-typed construction variable enters
val
as the key in the dictionary,
and None
as its value.
Using a tuple type to supply a key-value pair
only works for the special case of $CPPDEFINES
described above.
Although most combinations of types work without needing to know the details, some combinations do not make sense and Python raises an exception.
When using env.Append
to modify construction variables
which are path specifications (conventionally,
the names of such end in PATH
),
it is recommended to add the values as a list of strings,
even if you are only adding a single string.
The same goes for adding library names to $LIBS
.
env.Append(CPPPATH=["#/include"])
See also env.AppendUnique
,
env.Prepend
and env.PrependUnique
.
env
.AppendENVPath
(name, newpath, [envname, sep, delete_existing=False]
)
Append path elements specified by newpath
to the given search path string or list name
in mapping envname
in the construction environment.
Supplying envname
is optional:
the default is the execution environment $ENV
.
Optional sep
is used as the search path separator,
the default is the platform's separator (os.pathsep
).
A path element will only appear once.
Any duplicates in newpath
are dropped,
keeping the last appearing (to preserve path order).
If delete_existing
is False
(the default)
any addition duplicating an existing path element is ignored;
if delete_existing
is True
the existing value will
be dropped and the path element will be added at the end.
To help maintain uniqueness all paths are normalized (using
os.path.normpath
and
os.path.normcase
).
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
See also env.PrependENVPath
.
env
.AppendUnique
(key=val, [...], [delete_existing=False]
)
Append values to construction variables in the current construction environment,
maintaining uniqueness.
Works like env.Append
,
except that values that would become duplicates
are not added.
If delete_existing
is set to a true value, then for any duplicate,
the existing instance of val
is first removed,
then val
is appended,
having the effect of moving it to the end.
Example:
env.AppendUnique(CCFLAGS='-g', FOO=['foo.yyy'])
See also env.Append
,
env.Prepend
and env.PrependUnique
.
Builder
(action, [arguments]
), env
.Builder
(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
env.Builder
was called.
The
Builder
form delays all variable expansion
until after the Builder object is actually called.
CacheDir
(cache_dir, custom_class=None
), env
.CacheDir
(cache_dir, custom_class=None
)
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
env.CacheDir
limits the effect to targets built
through the specified construction environment.
Calling the global function
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 env.CacheDir
.
Caching behavior can be configured by passing a specialized cache
class as the optional custom_class
parameter.
This class must be a subclass of
SCons.CacheDir.CacheDir
.
SCons will internally invoke the custom class for performing
caching operations.
If the parameter is omitted or set to
None
, SCons will use the default
SCons.CacheDir.CacheDir
class.
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 useful 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 changes printing
to always show the action that would
have been used to build the file without caching.
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
option.
If the
--cache-force
option is used,
scons
will place a copy of
all
derived files into 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
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.
Note that (at this time) SCons provides no facilities for managing the derived-file cache. It is up to the developer to arrange for cache pruning, expiry, access control, etc. if needed.
Clean
(targets, files_or_dirs
), env
.Clean
(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
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
Clean
method, or as a list.
Clean
will also accept the return value of any of the construction environment
Builder methods.
Examples:
The related
NoClean
function overrides calling
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))
env
.Clone
([key=val, ...]
)Returns an independent copy of a construction environment. If there are any unrecognized keyword arguments specified, they are added as construction variables in the copy, overwriting any existing values for those keywords. See the manpage section "Construction Environments" for more details.
Example:
env2 = env.Clone() env3 = env.Clone(CCFLAGS='-g')
A list of tools
and a toolpath
may be specified,
as in the 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 env.MergeFlags
).
# create an environment for compiling programs that use wxWidgets wx_env = env.Clone(parse_flags='!wx-config --cflags --cxxflags')
The variables
keyword argument is also recognized, to allow (re)initializing
construction variables from a Variables
object.
Changed in version 4.8.0:
the variables
parameter was added.
Command
(target, source, action, [key=val, ...]
), env
.Command
(target, source, action, [key=val, ...]
)
Creates an anonymous builder and calls it,
thus recording action
to build target
from source
into the dependency tree.
This can be more convenient for a single special-case build
than having to define and add a new named Builder.
The
Command
function accepts the
source_scanner
and
target_scanner
keyword arguments which are used to specify
custom scanners for the specified sources or targets.
The value must be a Scanner object.
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 or function calls.
The
Command
function also accepts the
source_factory
and
target_factory
keyword arguments which are used to specify
factory functions to create SCons Nodes
from any sources or targets specified as strings.
If any sources or targets are already Node objects,
they are not further transformed even if
a factory is specified for them.
The default for each is the Entry
factory.
These four arguments, if given, are used in the creation of the Builder. Other Builder-specific keyword arguments are not recognized as such. See the manpage section "Builder Objects" for more information about how these arguments work in a Builder.
Any remaining keyword arguments are passed on to the generated builder when it is called, and behave as described in the manpage section "Builder Methods", in short: recognized arguments have their specified meanings, while the rest are used to override any same-named existing construction variables from the construction environment.
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
Dir
or
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.
Configure
(env, [custom_tests, conf_dir, log_file, config_h]
), env
.Configure
([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.
DebugOptions
([json]
)
Allows setting options for SCons debug options. Currently the only supported value is
json which sets the path to the json file created when
--debug=json
is set.
DebugOptions(json='#/build/output/scons_stats.json')
New in version 4.6.0.
Decider
(function
), env
.Decider
(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:
"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 by performing a checksum
on the dependency's contents using the selected hash function,
and comparing it to the checksum recorded the
last time the target was built.
content
is the default decider.
Changed in version 4.1:
The decider was renamed to content
since the hash function is now selectable.
The former name, MD5
,
can still be used as a synonym, but 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.
Changed in version 4.1:
The decider was renamed to content-timestamp
since the hash function is now selectable.
The former name, MD5-timestamp
,
can still be used as a synonym, but is deprecated.
"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.
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)
Default
(target[, ...]
), env
.Default
(target[, ...]
)
Specify default targets to the SCons target selection mechanism.
Any call to Default
will cause SCons to use the
defined default target list instead of
its built-in algorithm for determining default targets
(see the manpage section "Target Selection").
target
may be one or more strings,
a list of strings,
a NodeList
as returned by a Builder,
or None
.
A string target
may be the name of
a file or directory, or a target previously defined by a call to
Alias
(defining the alias later will still create
the alias, but it will not be recognized as a default).
Calls to Default
are additive.
A target
of
None
will clear any existing default target list;
subsequent calls to
Default
will add to the (now empty) default target list
like normal.
Both forms of this call affect the same global list of default targets; the construction environment method applies construction variable expansion to the targets.
The current list of targets added using
Default
is available in the
DEFAULT_TARGETS
list (see below).
Examples:
Default('foo', 'bar', 'baz') env.Default(['a', 'b', 'c']) hello = env.Program('hello', 'hello.c') env.Default(hello)
DefaultEnvironment
([key=value, ...]
)Instantiates and returns the global construction environment object. The Default Environment is used internally by SCons when executing a global function or the global form of a Builder method that requires access to a construction environment.
On the first call,
arguments are interpreted as for the Environment
function.
The Default Environment is a singleton;
subsequent calls to DefaultEnvironment
return
the already-constructed object,
and any keyword arguments are silently ignored.
The Default Environment can be modified after instantiation, similar to other construction environments, although some construction environment methods may be unavailable. Modifying the Default Environment has no effect on any other construction environment, either existing or newly constructed.
It is not necessary to explicitly call DefaultEnvironment
.
SCons instantiates the default environment automatically when the
build phase begins, if has not already been done.
However, calling it explicitly provides the opportunity to
affect and examine its contents.
Instantiation occurs even if nothing in the build system
appars to use it, due to internal uses.
If the project SConscript
files do not use global functions or Builders,
a small performance gain may be achieved by calling
DefaultEnvironment
with an empty tools list
(DefaultEnvironment(tools=[])
).
This avoids the tool initialization cost for the Default Environment,
which is mainly of interest in the test suite
where scons is launched repeatedly in a short time period.
Depends
(target, dependency
), env
.Depends
(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)
env
.Detect
(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 in the execution environment
(env
['ENV']['PATH']
).
On Windows systems, additionally applies the filename suffixes found in
the execution environment
(env
['ENV']['PATHEXT']
)
but will not include any such extension in the return value.
env.Detect
is a wrapper around env.WhereIs
.
env
.Dictionary
([vars]
)Returns a dictionary object containing the construction variables in the construction environment. If there are any arguments specified, the values of the specified construction variables 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')
Dir
(name, [directory]
), env
.Dir
(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 "Filesystem Nodes" for more information.
env
.Dump
([key, ...], [format=]
)
Serializes construction variables from the current construction environment
to a string.
The method supports the following formats specified by
format
,
which must be used a a keyword argument:
pretty
Returns a pretty-printed representation of the variables (this is the default). The variables will be presented in Python dict form.
json
Returns a JSON-formatted string representation of the variables. The variables will be presented as a JSON object literal, the JSON equivalent of a Python dict.
If no key
is supplied,
all the construction variables are serialized.
If one or more keys are supplied,
only those keys and their values are serialized.
Changed in NEXT_VERSION:
More than one key
can be specified.
The returned string always looks like a dict (or JSON equivalent);
previously a single key serialized only the value,
not the key with the value.
This SConstruct:
env = Environment() print(env.Dump('CCCOM')) print(env.Dump('CC', 'CCFLAGS', format='json'))
will print something like:
{'CCCOM': '$CC -o $TARGET -c $CFLAGS $CCFLAGS $_CCCOMCOM $SOURCES'} { "CC": "gcc", "CCFLAGS": [] }
While this SConstruct:
env = Environment() print(env.Dump())
will print something like:
{ 'AR': 'ar', 'ARCOM': '$AR $ARFLAGS $TARGET $SOURCES\n$RANLIB $RANLIBFLAGS $TARGET', 'ARFLAGS': ['r'], 'AS': 'as', 'ASCOM': '$AS $ASFLAGS -o $TARGET $SOURCES', 'ASFLAGS': [], ...
EnsurePythonVersion
(major, minor
)
Ensure that the Python version is at least
major
.minor
.
This function will
print out an error message and exit SCons with a non-zero exit code if the
actual Python version is not late enough.
Example:
EnsurePythonVersion(2,2)
EnsureSConsVersion
(major, minor, [revision]
)
Ensure that the SCons version is at least
major.minor
,
or
major.minor.revision
.
if
revision
is specified.
This function will
print out an error message and exit SCons with a non-zero exit code if the
actual SCons version is not late enough.
Examples:
EnsureSConsVersion(0,14) EnsureSConsVersion(0,96,90)
Environment
([key=value, ...]
), env
.Environment
([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 specially recognized and do not lead to
construction variable creation.
See the manpage section "Construction Environments" for more details.
Execute
(action, [actionargs ...]
), env
.Execute
(action, [actionargs ...]
)
Executes an Action.
action
may be an Action object
or it may be a command-line string,
list of commands,
or executable Python function,
each of which will first be converted
into an Action object
and then executed.
Any additional arguments to Execute
are passed on to the Action
factory function
which actually creates the Action object
(see the manpage section Action Objects
for a description). Example:
Execute(Copy('file.out', 'file.in'))
Execute
performs its action immediately,
as part of the SConscript-reading phase.
There are no sources or targets declared in an
Execute
call, so any objects it manipulates
will not be tracked as part of the SCons dependency graph.
In the example above, neither
file.out
nor
file.in
will be tracked objects.
Execute
returns the exit value of the command
or return value of the Python function.
scons
prints an error message if the executed
action
fails (exits with or returns a non-zero value),
however it does
not,
automatically terminate the build for such a failure.
If you want the build to stop in response to a failed
Execute
call,
you must explicitly check for a non-zero return value:
if Execute("mkdir sub/dir/ectory"): # The mkdir failed, don't try to build. Exit(1)
Exit
([value]
)
This tells
scons
to exit immediately
with the specified
value
.
A default exit value of
0
(zero)
is used if no value is specified.
Export
([vars...], [key=value...]
), env
.Export
([vars...], [key=value...]
)
Exports variables for sharing with other SConscript files.
The variables are added to a global collection where
they can be imported by other SConscript files.
vars
may be one or more
strings, or a list of strings. If any string
contains whitespace, it is split automatically
into individual strings. Each string must
match the name of a variable that is in scope
during evaluation of the current SConscript file,
or an exception is raised.
A vars
argument
may also be a dictionary or
individual keyword arguments;
in accordance with Python syntax rules,
keyword arguments must come after any
non-keyword arguments.
The dictionary/keyword form can be used
to map the local name of a variable to
a different name to be used for imports.
See the Examples for an illustration of the syntax.
Export
calls are cumulative. Specifying a previously
exported variable will replace the previous value in the collection.
Both local variables and global variables can be exported.
To use an exported variable, an SConscript must
call Import
to bring it into its own scope.
Importing creates an additional reference to the object that
was originally exported, so if that object is mutable,
changes made will be visible to other users of that object.
Examples:
env = Environment() # Make env available for all SConscript files to Import(). Export("env") package = 'my_name' # Make env and package available for all SConscript files:. Export("env", "package") # Make env and package available for all SConscript files: Export(["env", "package"]) # Make env available using the name debug: Export(debug=env) # Make env available using the name debug: Export({"debug": env})
Note that the
SConscript
function also supports an exports
argument that allows exporting one or more variables
to the SConscript files invoked by that call (only).
See the description of that function for details.
File
(name, [directory]
), env
.File
(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 "Filesystem Nodes" for more information.
FindFile
(file, dirs
), env
.FindFile
(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'])
FindInstalledFiles
(), env
.FindInstalledFiles
()
Returns the list of targets set up by the
Install
or
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()
FindPathDirs
(variable
)
Returns a function
(actually a callable Python object)
intended to be used as the
path_function
of a Scanner object.
The returned object will look up the specified
variable
in a construction environment
and treat the construction variable's value as a list of
directory paths that should be searched
(like
$CPPPATH
,
$LIBPATH
,
etc.).
Note that use of
FindPathDirs
is generally preferable to
writing your own
path_function
for the following reasons:
1) The returned list will contain all appropriate directories
found in source trees
(when
VariantDir
is used)
or in code repositories
(when
Repository
or the
-Y
option are used).
2) scons will identify expansions of
variable
that evaluate to the same list of directories as,
in fact, the same list,
and avoid re-scanning the directories for files,
when possible.
Example:
def my_scan(node, env, path, arg): # Code to scan file contents goes here... return include_files scanner = Scanner(name = 'myscanner', function = my_scan, path_function = FindPathDirs('MYPATH'))
FindSourceFiles
(node='"."'
), env
.FindSourceFiles
(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.
Flatten
(sequence
), env
.Flatten
(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))
GetBuildFailures
()
Returns a list of exceptions for the
actions that failed while
attempting to build targets.
Each element in the returned list is a
BuildError
object
with the following attributes
that record various aspects
of the build failure:
.node
The node that was being built
when the build failure occurred.
.status
The numeric exit status
returned by the command or Python function
that failed when trying to build the
specified Node.
.errstr
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.)
.filename
The name of the file or
directory that actually caused the failure.
This may be different from the
.node
attribute.
For example,
if an attempt to build a target named
sub/dir/target
fails because the
sub/dir
directory could not be created,
then the
.node
attribute will be
sub/dir/target
but the
.filename
attribute will be
sub/dir
.
.executor
The SCons Executor object
for the target Node
being built.
This can be used to retrieve
the construction environment used
for the failed action.
.action
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.
.command
The actual expanded command that was executed and failed,
after expansion of
$TARGET
,
$SOURCE
,
and other construction variables.
Note that the
GetBuildFailures
function
will always return an empty list
until any build failure has occurred,
which means that
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
atexit.register
()
function.
Example:
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)
GetBuildPath
(file, [...]
), env
.GetBuildPath
(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.
GetLaunchDir
()
Returns the absolute path name of the directory from which
scons
was initially invoked.
This can be useful when using the
-u
,
-U
or
-D
options, which internally
change to the directory in which the
SConstruct
file is found.
GetOption
(name
), env
.GetOption
(name
)
Query the value of settable options which may have been set
on the command line, via option defaults,
or by using the SetOption
function.
The value of the option is returned in a type matching how the
option was declared - see the documentation of the
corresponding command line option for information about each specific
option.
name
can be an entry from the following table,
which shows the corresponding command line arguments
that could affect the value.
name
can be also be the destination
variable name from a project-specific option added using the
AddOption
function, as long as that addition has been
processed prior to the GetOption
call in the SConscript
files.
Query name | Command-line options | Notes |
---|---|---|
cache_debug | --cache-debug | |
cache_disable |
--cache-disable ,
--no-cache
| |
cache_force |
--cache-force ,
--cache-populate
| |
cache_readonly | --cache-readonly | |
cache_show | --cache-show | |
clean |
-c ,
--clean ,
--remove
| |
climb_up |
-D
-U
-u
--up
--search_up
| |
config | --config | |
debug | --debug | |
directory | -C , --directory | |
diskcheck | --diskcheck | |
duplicate | --duplicate | |
enable_virtualenv | --enable-virtualenv | |
experimental | --experimental | since 4.2 |
file |
-f ,
--file ,
--makefile ,
--sconstruct
| |
hash_format | --hash-format | since 4.2 |
help | -h , --help | |
ignore_errors | -i , --ignore-errors | |
ignore_virtualenv | --ignore-virtualenv | |
implicit_cache | --implicit-cache | |
implicit_deps_changed | --implicit-deps-changed | |
implicit_deps_unchanged | --implicit-deps-unchanged | |
include_dir | -I , --include-dir | |
install_sandbox | --install-sandbox | Available only if the install tool has been called |
keep_going | -k , --keep-going | |
max_drift | --max-drift | |
md5_chunksize |
--hash-chunksize ,
--md5-chunksize
| --hash-chunksize since 4.2 |
no_exec |
-n ,
--no-exec ,
--just-print ,
--dry-run ,
--recon
| |
no_progress | -Q | |
num_jobs | -j , --jobs | |
package_type | --package-type | Available only if the packaging tool has been called |
profile_file | --profile | |
question | -q , --question | |
random | --random | |
repository |
-Y ,
--repository ,
--srcdir
| |
silent |
-s ,
--silent ,
--quiet
| |
site_dir | --site-dir , --no-site-dir | |
stack_size | --stack-size | |
taskmastertrace_file | --taskmastertrace | |
tree_printers | --tree | |
warn | --warn , --warning |
GetSConsVersion
()Returns the current SCons version in the form of a Tuple[int, int, int], representing the major, minor, and revision values respectively. Added in 4.8.0.
Glob
(pattern, [ondisk=True, source=False, strings=False, exclude=None]
), env
.Glob
(pattern, [ondisk=True, source=False, strings=False, exclude=None]
)
Returns a possibly empty list of Nodes (or strings) that match
pathname specification pattern
.
pattern
can be absolute,
top-relative,
or (most commonly) relative to the directory of the current
SConscript
file.
Glob
matches both files stored on disk and Nodes
which SCons already knows about, even if any corresponding
file is not currently stored on disk.
The evironment method form (env.Glob
)
performs string substition on
pattern
and returns whatever matches the resulting expanded pattern.
The results are sorted, unlike for the similar Python
glob.glob
function,
to ensure build order will be stable.
pattern
can contain POSIX-style shell metacharacters for matching:
Pattern | Meaning |
---|---|
* | matches everything |
? | matches any single character |
[seq] | matches any character in seq (can be a list or a range). |
[!seq] | matches any character not in seq |
For a literal match, wrap the metacharacter in brackets to
escape the normal behavior.
For example, '[?]'
matches the character
'?'
.
Filenames starting with a dot are specially handled - they can only be matched by patterns that start with a dot (or have a dot immediately following a pathname separator character, or slash), they are not not matched by the metacharacters. Metacharacter matches also do not span directory separators.
Glob
understands repositories
(see the
Repository
function)
and source directories
(see the
VariantDir
function)
and returns a Node (or string, if so configured) match
in the local (SConscript) directory
if a matching Node is found
anywhere in a corresponding
repository or source directory.
If the optional
ondisk
argument evaluates false,
the search for matches on disk is disabled,
and only matches from
already-configured File or Dir Nodes are returned.
The default is to return Nodes for
matches on disk as well.
If the optional
source
argument evaluates true,
and the local directory is a variant directory,
then Glob
returnes Nodes from
the corresponding source directory,
rather than the local directory.
If the optional
strings
argument evaluates true,
Glob
returns matches as strings, rather than Nodes.
The returned strings will be relative to
the local (SConscript) directory.
(Note that while this may make it easier to perform
arbitrary manipulation of file names,
it loses the context SCons would have in the Node,
so if the returned strings are
passed to a different
SConscript
file,
any Node translation there will be relative
to that
SConscript
directory,
not to the original
SConscript
directory.)
The optional
exclude
argument may be set to a pattern or a list of patterns
descibing files or directories
to filter out of the match list.
Elements matching a least one specified pattern will be excluded.
These patterns use the same syntax as for
pattern
.
Examples:
Program("foo", Glob("*.c")) Zip("/tmp/everything", Glob(".??*") + Glob("*")) sources = Glob("*.cpp", exclude=["os_*_specific_*.cpp"]) \ + Glob("os_%s_specific_*.cpp" % currentOS)
Help
(text, append=False, local_only=False
), env
.Help
(text, append=False, local_only=False
)
Adds text
to the help message shown when
scons is called with the
-h
or --help
argument.
On the first call to Help
,
if append
is False
(the default), any existing help text is discarded.
The default help text is the help for the scons
command itself plus help collected from any
project-local AddOption
calls.
This is the help printed if Help
has never been called.
If append
is True
,
text
is appended to
the existing help text.
If local_only
is also True
(the default is False
),
the project-local help from AddOption
calls is preserved
in the help message but the scons command help is not.
Subsequent calls to
Help
ignore the keyword arguments
append
and
local_only
and always append to the existing help text.
Changed in 4.6.0: added local_only
.
Ignore
(target, dependency
), env
.Ignore
(target, dependency
)
Ignores dependency
when deciding if
target
needs to be rebuilt.
target
and
dependency
can each be a single filename or Node
or a list of filenames or Nodes.
Ignore
can also be used to
remove a target from the default build
by specifying the directory the target will be built in as
target
and the file you want to skip selecting for building as
dependency
.
Note that this only removes the target from
the default target selection algorithm:
if it is a dependency of another object being
built SCons still builds it normally.
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')
Import
(vars...
), env
.Import
(vars...
)
Imports variables into the scope of the current SConscript file.
vars
must be strings representing names of variables
which have been previously exported either by the
Export
function or by the
exports
argument to the
SConscript
function.
Variables exported by the
SConscript
call
take precedence.
Multiple variable names can be passed to
Import
as separate arguments, as a list of strings,
or as words in a space-separated string.
The wildcard "*"
can be used to import all
available variables.
If the imported variable is mutable, changes made locally will be reflected in the object the variable is bound to. This allows subsidiary SConscript files to contribute to building up, for example, a construction environment.
Examples:
Import("env") Import("env", "variable") Import(["env", "variable"]) Import("*")
Literal
(string
), env
.Literal
(string
)
The specified
string
will be preserved as-is
and not have construction variables expanded.
Local
(targets
), env
.Local
(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.
env
.MergeFlags
(arg, [unique]
)
Merges values from
arg
into construction variables in env
.
If arg
is a dictionary,
each key-value pair represents a
construction variable name and the corresponding flags to merge.
If arg
is not a dictionary,
MergeFlags
attempts to convert it to one
before the values are merged.
env.ParseFlags
is used for this,
so values to be converted are subject to the
same limitations:
ParseFlags
has knowledge of which construction variables certain
flags should go to, but not all;
and only for GCC and compatible compiler chains.
arg
must be a single object,
so to pass multiple strings,
enclose them in a list.
If unique
is true (the default),
duplicate values are not retained.
In case of duplication,
any construction variable names that end in
PATH
keep the left-most value so the
path searcb order is not altered.
All other construction variables keep
the right-most value.
If unique
is false,
values are appended even if they are duplicates.
Examples:
# Add an optimization flag to $CCFLAGS. env.MergeFlags({'CCFLAGS': '-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 # for two distinct packages and merge into the construction variables. env.MergeFlags( [ '-O3', '!pkg-config gtk+-2.0 --cflags --libs', '!pkg-config libpng12 --cflags --libs', ] )
NoCache
(target, ...
), env
.NoCache
(target, ...
)
Specifies a list of files which should
not
be cached whenever the
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
NoCache
method, or as a list.
NoCache
will also accept the return value of any of the construction environment
Builder methods.
Calling
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'))
NoClean
(target, ...
), env
.NoClean
(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
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
NoClean
method, or as a list.
NoClean
will also accept the return value of any of the construction environment
Builder methods.
Calling
NoClean
for a target overrides calling
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'))
env
.ParseConfig
(command, [function, unique]
)
Updates the current construction environment with the values extracted
from the output of running external command
,
by passing it to a helper function
.
command
may be a string
or a list of strings representing the command and
its arguments.
If function
is omitted or None
,
env.MergeFlags
is used.
By default,
duplicate values are not
added to any construction variables;
you can specify
unique=False
to allow duplicate values to be added.
command
is executed using the
SCons execution environment (that is, the construction variable
$ENV
in the current construction environment).
If command
needs additional information
to operate properly, that needs to be set in the execution environment.
For example, pkg-config
may need a custom value set in the PKG_CONFIG_PATH
environment variable.
env.MergeFlags
needs to understand
the output produced by command
in order to distribute it to appropriate construction variables.
env.MergeFlags
uses a separate function to
do that processing -
see env.ParseFlags
for the details, including a
a table of options and corresponding construction variables.
To provide alternative processing of the output of
command
,
you can suppply a custom
function
,
which must accept three arguments:
the construction environment to modify,
a string argument containing the output from running
command
,
and the optional
unique
flag.
ParseDepends
(filename, [must_exist, only_one]
), env
.ParseDepends
(filename, [must_exist, only_one]
)
Parses the contents of 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 filename
does not exist.
The optional
must_exist
argument may be set to True
to have SCons
raise an exception if the file does not exist,
or is otherwise inaccessible.
The optional
only_one
argument may be set to True
to have SCons raise an exception
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.
filename
and all of the files listed therein
will be interpreted relative to
the directory of the
SConscript
file which calls the
ParseDepends
function.
env
.ParseFlags
(flags, ...
)
Parses one or more strings containing
typical command-line flags for GCC-style tool chains
and returns a dictionary with the flag values
separated into the appropriate SCons construction variables.
Intended as a companion to the
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
env.MergeFlags
will call this method if its argument is not a dictionary,
so it is usually not necessary to call
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.
This can be used to call a *-config
command typical of the POSIX programming environment
(for example,
pkg-config).
Note that such a command is executed using the
SCons execution environment;
if the command needs additional information,
that information needs to be explicitly provided.
See ParseConfig
for more details.
Flag values are translated according 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 -fsanitize 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 -stdlib= CXXFLAGS -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
$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')
Platform
(plat
), env
.Platform
(plat
)
When called as a global function,
returns a callable platform object
selected by plat
(defaults to the detected platform for the
current system)
that can be used to initialize
a construction environment by passing it as the
platform
keyword argument to the
Environment
function.
Example:
env = Environment(platform=Platform('win32'))
When called as a method of an environment,
calls the platform object indicated by
plat
to update that environment.
env.Platform('posix')
See the manpage section "Construction Environments" for more details.
Precious
(target, ...
), env
.Precious
(target, ...
)
Marks target
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 a single call,
and may be strings and/or nodes.
Returns a list of the affected target nodes.
env
.Prepend
(key=val, [...]
)
Prepend values to construction variables in the current construction environment,
Works like env.Append
(see for details),
except that values are added to the front,
rather than the end, of any existing value of the construction variable
Example:
env.Prepend(CCFLAGS='-g ', FOO=['foo.yyy'])
See also env.Append
,
env.AppendUnique
and env.PrependUnique
.
env
.PrependENVPath
(name, newpath, [envname, sep, delete_existing=True]
)
Prepend path elements specified by newpath
to the given search path string or list name
in mapping envname
in the construction environment.
Supplying envname
is optional:
the default is the execution environment $ENV
.
Optional sep
is used as the search path separator,
the default is the platform's separator (os.pathsep
).
A path element will only appear once.
Any duplicates in newpath
are dropped,
keeping the first appearing (to preserve path order).
If delete_existing
is False
any addition duplicating an existing path element is ignored;
if delete_existing
is True
(the default) the existing value will
be dropped and the path element will be inserted at the beginning.
To help maintain uniqueness all paths are normalized (using
os.path.normpath
and
os.path.normcase
).
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
See also env.AppendENVPath
.
env
.PrependUnique
(key=val, [...], [delete_existing=False]
)
Prepend values to construction variables in the current construction environment,
maintaining uniqueness.
Works like env.Append
,
except that values are added to the front,
rather than the end, of the construction variable,
and values that would become duplicates
are not added.
If delete_existing
is set to a true value, then for any duplicate,
the existing instance of val
is first removed,
then val
is inserted,
having the effect of moving it to the front.
Example:
env.PrependUnique(CCFLAGS='-g', FOO=['foo.yyy'])
See also env.Append
,
env.AppendUnique
and env.Prepend
.
Progress
(callable, [interval]
), Progress
(string, [interval, file, overwrite]
), Progress
(list_of_strings, [interval, file, overwrite]
)Allows SCons to show progress made during the build by displaying a string or calling a function while evaluating Nodes (e.g. files).
If the first specified argument is a Python callable
(a function or an object that has a
__call__
method),
the function will be called
once every
interval
times a Node is evaluated (default 1
).
The callable will be passed the evaluated Node
as its only argument.
(For future compatibility,
it's a good idea to also add
*args
and
**kwargs
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.)
An example of a simple custom progress function that prints a string containing the Node name every 10 Nodes:
def my_progress_function(node, *args, **kwargs): print('Evaluating node %s!' % node) Progress(my_progress_function, interval=10)
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
\r
(a carriage return)
at the end so that the string
will overwrite itself on a display:
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)
If the first argument to
Progress
is a string or list of strings,
it is taken as text to be displayed every
interval
evaluated Nodes.
If the first argument is a list of strings,
then each string in the list will be displayed
in rotating fashion every
interval
evaluated Nodes.
The default is to print the string on standard output.
An alternate output stream
may be specified with the
file
keyword argument, which the
caller must pass already opened.
The following will print a series of dots on the error output, one dot for every 100 evaluated Nodes:
import sys Progress('.', interval=100, file=sys.stderr)
If the string contains the verbatim substring
$TARGET;
,
it will be replaced with the Node.
Note that, for performance reasons, this is
not
a regular SCons variable substition,
so you can not use other variables
or use curly braces.
The following example will print the name of
every evaluated Node,
using a carriage return)
(\r
)
to cause each line to overwritten by the next line,
and the
overwrite
keyword argument (default False
)
to make sure the previously-printed
file name is overwritten with blank spaces:
import sys Progress('$TARGET\r', overwrite=True)
A list of strings can be used to implement a "spinner" on the user's screen as follows, changing every five evaluated Nodes:
Progress(['-\r', '\\\r', '|\r', '/\r'], interval=5)
Pseudo
(target, ...
), env
.Pseudo
(target, ...
)
Marks target
as a pseudo target,
not representing the production of any physical target file.
If any pseudo target
does exist,
SCons will abort the build with an error.
Multiple targets can be passed in a single call,
and may be strings and/or Nodes.
Returns a list of the affected target nodes.
Pseudo
may be useful in conjuction with a builder
call (such as Command
) which does not create a physical target,
and the behavior if the target accidentally existed would be incorrect.
This is similar in concept to the GNU make
.PHONY
target.
SCons also provides a powerful target alias capability
(see Alias
) which may provide more flexibility
in many situations when defining target names that are not directly built.
PyPackageDir
(modulename
), env
.PyPackageDir
(modulename
)
Finds the location of modulename
,
which can be a string or a sequence of strings,
each representing the name of a Python module.
Construction variables are expanded in
modulename
.
Returns a Directory Node (see Dir
),
or a list of Directory Nodes if
modulename
is a sequence.
None
is returned for any module not found.
When a Tool module which is installed as a
Python module is used, you need
to specify a toolpath
argument to
Tool
,
Environment
or Clone
,
as tools outside the standard project locations
(site_scons/site_tools
)
will not be found otherwise.
Using PyPackageDir
allows this path to be
discovered at runtime instead of hardcoding the path.
Example:
env = Environment( tools=["default", "ExampleTool"], toolpath=[PyPackageDir("example_tool")] )
env
.Replace
(key=val, [...]
)Replaces construction variables in the Environment with the specified keyword arguments.
Example:
env.Replace(CCFLAGS='-g', FOO='foo.xxx')
Repository
(directory
), env
.Repository
(directory
)
Specifies that
directory
is a repository to be searched for files.
Multiple calls to
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
Local
method.
Requires
(target, prerequisite
), env
.Requires
(target, prerequisite
)
Specifies an order-only relationship
between target
and prerequisite
.
The prerequisites
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.
target
and
prerequisite
may each
be a string or Node, or a list of strings or Nodes.
If there are multiple
target
values,
the prerequisite(s) are added to each one.
Returns a list of the affected target nodes.
Example:
env.Requires('foo', 'file-that-must-be-built-before-foo')
Return
([vars..., stop=True]
)
Return to the calling SConscript, optionally
returning the values of variables named in
vars
.
Multiple strings contaning variable names may be passed to
Return
. A string containing white space
is split into individual variable names.
Returns the value if one variable is specified,
else returns a tuple of values.
Returns an empty tuple if vars
is omitted.
By default Return
stops processing the current SConscript
and returns immediately.
The optional
stop
keyword argument
may be set to a false value
to continue processing the rest of the SConscript
file after the
Return
call (this was the default behavior prior to SCons 0.98.)
However, the values returned
are still the values of the variables in the named
vars
at the point
Return
was called.
Examples:
# Returns no values (evaluates False) Return() # Returns the value of the 'foo' Python variable. Return("foo") # Returns the values of the Python variables 'foo' and 'bar'. Return("foo", "bar") # Returns the values of Python variables 'val1' and 'val2'. Return('val1 val2')
Scanner
(function, [name, argument, skeys, path_function, node_class, node_factory, scan_check, recursive]
), env
.Scanner
(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.
SConscript
(scriptnames, [exports, variant_dir, duplicate, must_exist]
), env
.SConscript
(scriptnames, [exports, variant_dir, duplicate, must_exist]
), SConscript
(dirs=subdirs, [name=scriptname, exports, variant_dir, duplicate, must_exist]
), env
.SConscript
(dirs=subdirs, [name=scriptname, exports, variant_dir, duplicate, must_exist]
)
Executes subsidiary SConscript (build configuration) file(s).
There are two ways to call the
SConscript
function.
The first calling style is to supply
one or more SConscript file names
as the first positional argument,
which can be a string or a list of strings.
If there is a second positional argument,
it is treated as if the
exports
keyword argument had been given (see below).
Examples:
SConscript('SConscript') # run SConscript in the current directory SConscript('src/SConscript') # run SConscript in the src directory SConscript(['src/SConscript', 'doc/SConscript']) SConscript(Split('src/SConscript doc/SConscript')) config = SConscript('MyConfig.py')
The second calling style is to omit the positional argument naming
the script and instead specify directory names using the
dirs
keyword argument.
The value can be a string or list of strings.
In this case,
scons
will execute a subsidiary configuration file named
SConscript
(by default)
in each of the specified directories.
You may specify a name other than
SConscript
by supplying an optional
name
=scriptname
keyword argument.
The first three examples below have the same effect
as the first three examples above:
SConscript(dirs='.') # run SConscript in the current directory SConscript(dirs='src') # run SConscript in the src directory SConscript(dirs=['src', 'doc']) SConscript(dirs=['sub1', 'sub2'], name='MySConscript')
The optional
exports
keyword argument specifies variables to make available
for use by the called SConscripts,
which are evaluated in an isolated context
and otherwise do not have access to local variables
from the calling SConscript.
The value may be a string or list of strings representing
variable names, or a dictionary mapping local names to
the names they can be imported by.
For the first (scriptnames) calling style,
a second positional argument will also be interpreted as
exports
;
the second (directory) calling style accepts no
positional arguments and must use the keyword form.
These variables are locally exported only to the called
SConscript file(s), and take precedence over any same-named
variables in the global pool managed by the
Export
function.
The subsidiary SConscript files
must use the
Import
function to import the variables into their local scope.
Examples:
foo = SConscript('sub/SConscript', exports='env') SConscript('dir/SConscript', exports=['env', 'variable']) SConscript(dirs='subdir', exports='env variable') SConscript(dirs=['one', 'two', 'three'], exports='shared_info')
If the optional
variant_dir
argument is present, it causes an effect equivalent to the
VariantDir
function,
but in effect only within the scope of the SConscript
call.
The variant_dir
argument is interpreted relative to the directory of the
calling SConscript file.
The source directory is the directory in which the
called SConscript
file resides and the SConscript
file is evaluated as if it were in the
variant_dir
directory. Thus:
SConscript('src/SConscript', variant_dir='build')
is equivalent to:
VariantDir('build', 'src') SConscript('build/SConscript')
If the sources are in the same directory as the
SConstruct
,
SConscript('SConscript', variant_dir='build')
is equivalent to:
VariantDir('build', '.') SConscript('build/SConscript')
The optional
duplicate
argument is
interpreted as for VariantDir
.
If the variant_dir
argument
is omitted, the duplicate
argument is ignored.
See the description of
VariantDir
for additional details and restrictions.
If the optional
must_exist
is True
(the default),
an exception is raised if a requested
SConscript file is not found.
To allow missing scripts to be silently ignored
(the default behavior prior to SCons version 3.1),
pass
must_exist=False
in the SConscript
call.
Changed in 4.6.0: must_exist
now defaults to True
.
Here are some composite examples:
# collect the configuration information and use it to build src and doc shared_info = SConscript('MyConfig.py') SConscript('src/SConscript', exports='shared_info') SConscript('doc/SConscript', exports='shared_info')
# build debugging and production versions. SConscript # can use Dir('.').path to determine variant. SConscript('SConscript', variant_dir='debug', duplicate=0) SConscript('SConscript', variant_dir='prod', duplicate=0)
# build debugging and production versions. SConscript # is passed flags to use. opts = { 'CPPDEFINES' : ['DEBUG'], 'CCFLAGS' : '-pgdb' } SConscript('SConscript', variant_dir='debug', duplicate=0, exports=opts) opts = { 'CPPDEFINES' : ['NODEBUG'], 'CCFLAGS' : '-O' } SConscript('SConscript', variant_dir='prod', duplicate=0, exports=opts)
# build common documentation and compile for different architectures SConscript('doc/SConscript', variant_dir='build/doc', duplicate=0) SConscript('src/SConscript', variant_dir='build/x86', duplicate=0) SConscript('src/SConscript', variant_dir='build/ppc', duplicate=0)
SConscript
returns the values of any variables
named by the executed SConscript file(s) in arguments
to the Return
function.
If a single SConscript
call causes multiple scripts to
be executed, the return value is a tuple containing
the returns of each of the scripts. If an executed
script does not explicitly call Return
, it returns
None
.
SConscriptChdir
(value
)
By default,
scons
changes its working directory
to the directory in which each
subsidiary SConscript file lives
while reading and processing that script.
This behavior may be disabled
by specifying an argument which
evaluates false, 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:
SConscriptChdir(False) SConscript('foo/SConscript') # will not chdir to foo SConscriptChdir(True) SConscript('bar/SConscript') # will chdir to bar
SConsignFile
([name, dbm_module]
), env
.SConsignFile
([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 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)
env
.SetDefault
(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'
SetOption
(name, value
), env
.SetOption
(name, value
)
Sets scons option variable name
to value
.
These options are all also settable via
command-line options but the variable name
may differ from the command-line option name -
see the table for correspondences.
A value set via command-line option will take
precedence over one set with SetOption
, which
allows setting a project default in the scripts and
temporarily overriding it via command line.
SetOption
calls can also be placed in the
site_init.py
file.
See the documentation in the manpage for the
corresponding command line option for information about each specific option.
The value
parameter is mandatory,
for option values which are boolean in nature
(that is, the command line option does not take an argument)
use a value
which evaluates to true (e.g. True
,
1
) or false (e.g. False
,
0
).
Options which affect the reading and processing of SConscript files
are not settable using SetOption
since those files must
be read in order to find the SetOption
call in the first place.
For project-specific options (sometimes called
local options)
added via an AddOption
call,
SetOption
is available only after the
AddOption
call has completed successfully,
and only if that call included the
settable=True
argument.
The settable variables with their associated command-line options are:
Settable name | Command-line options | Notes |
---|---|---|
clean |
-c ,
--clean ,
--remove
| |
diskcheck | --diskcheck | |
duplicate | --duplicate | |
experimental | --experimental | since 4.2 |
hash_chunksize | --hash-chunksize |
Actually sets md5_chunksize .
since 4.2
|
hash_format | --hash-format | since 4.2 |
help | -h , --help | |
implicit_cache | --implicit-cache | |
implicit_deps_changed | --implicit-deps-changed |
Also sets implicit_cache .
(settable since 4.2)
|
implicit_deps_unchanged | --implicit-deps-unchanged |
Also sets implicit_cache .
(settable since 4.2)
|
max_drift | --max-drift | |
md5_chunksize | --md5-chunksize | |
no_exec |
-n ,
--no-exec ,
--just-print ,
--dry-run ,
--recon
| |
no_progress | -Q | See [a] |
num_jobs | -j , --jobs | |
random | --random | |
silent |
-s ,
--silent ,
--quiet
| |
stack_size | --stack-size | |
warn | --warn | |
[a] If |
Example:
SetOption('max_drift', 0)
SideEffect
(side_effect, target
), env
.SideEffect
(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
Clean
or
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.
Split
(arg
), env
.Split
(arg
)
If arg
is a string,
splits on whitespace and returns a list of
strings without whitespace.
This mode is the most common case,
and can be used to split a list of filenames
(for example) rather than having to type them as a
list of individually quoted words.
If arg
is a list or tuple
returns the list or tuple unchanged.
If arg
is any other type of object,
returns a list containing just the object.
These non-string cases do not actually do any spliting,
but allow an argument variable to be passed to
Split
without having to first check its type.
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 """)
env
.subst
(input, [raw, target, source, conv]
)
Performs construction variable interpolation
(substitution)
on input
,
which can be a string or a sequence.
Substitutable elements take the form
${
,
although if there is no ambiguity in recognizing the element,
the braces can be omitted.
A literal $ can be entered by
using $$.
expression
}
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 additionally discard
all characters between any
$(
and
$)
pairs
(as is done for signature calculation).
If 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
$TARGET
,
$TARGETS
,
$SOURCE
and
$SOURCES
to be available for expansion.
This is usually necessary if you are
calling
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 a Python
lambda expression 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)
Tag
(node, tags
)
Annotates file or directory Nodes with
information about how the
Package
Builder should package those files or directories.
All Node-level tags are optional.
Examples:
# makes sure the built library will be installed with 644 file access mode Tag(Library('lib.c'), UNIX_ATTR="0o644") # marks file2.txt to be a documentation file Tag('file2.txt', DOC)
Tool
(name, [toolpath, key=value, ...]
), env
.Tool
(name, [toolpath, key=value, ...]
)
Locates the tool specification module name
and returns a callable tool object for that tool.
When the environment method (env.Tool
) form is used,
the tool object is automatically called before the method returns
to update env
,
and name
is
appended to the $TOOLS
construction variable in that environment.
When the global function Tool
form is used,
the tool object is constructed but not called,
as it lacks the context of an environment to update,
and the returned object needs to be used to arrange for the call.
The tool module is searched for in the tool search paths (see the
Tools section in the manual page
for details)
and in any paths specified by the optional
toolpath
parameter,
which must be a list of strings.
If toolpath
is omitted,
the toolpath
supplied when the environment was created,
if any, is used.
Any remaining keyword arguments are saved in
the tool object,
and will be passed to the tool module's
generate
function
when the tool object is actually called.
The generate
function
can update the construction environment with construction variables and arrange
any other initialization
needed to use the mechanisms that tool describes,
and can use these extra arguments to help
guide its actions.
Changed in version 4.2:
env.Tool
now returns the tool object,
previously it did not return (i.e. returned None
).
Examples:
env.Tool('gcc') env.Tool('opengl', toolpath=['build/tools'])
The returned tool object can be passed to an
Environment
or Clone
call
as part of the tools
keyword argument,
in which case the tool is applied to the environment being constructed,
or it can be called directly,
in which case a construction environment to update must be
passed as the argument.
Either approach will also update the
$TOOLS
construction variable.
Examples:
env = Environment(tools=[Tool('msvc')]) env = Environment() msvctool = Tool('msvc') msvctool(env) # adds 'msvc' to the TOOLS variable gltool = Tool('opengl', toolpath = ['tools']) gltool(env) # adds 'opengl' to the TOOLS variable
ValidateOptions
([throw_exception=False]
)
Check that all the options specified on the command line are either
SCons built-in options or defined via calls to AddOption
.
SCons will eventually fail on unknown options anyway, but calling
this function allows the build to "fail fast" before executing
expensive logic later in the build.
This function should only be called after the last AddOption
call in your SConscript
logic.
Be aware that some tools call AddOption
, if you are getting
error messages for arguments that they add, you will need to ensure
that those tools are loaded before calling ValidateOptions
.
If there are any unknown command line options, ValidateOptions
prints an error message and exits with an error exit status.
If the optional throw_exception
argument is
True
(default is False
),
a SConsBadOptionError
is raised,
giving an opportunity for the SConscript
logic to catch that
exception and handle invalid options appropriately. Note that
this exception name needs to be imported (see the example below).
A common build problem is typos (or thinkos) - a user enters an option that is just a little off the expected value, or perhaps a different word with a similar meaning. It may be useful to abort the build before going too far down the wrong path. For example:
$ scons --compilers=mingw
# the correct flag is --compiler
Here SCons could go off and run a bunch of configure steps with
the default value of --compiler
, since the
incorrect command line did not actually supply a value to it,
costing developer time to track down why the configure logic
made the "wrong" choices. This example shows catching this:
from SCons.Script.SConsOptions import SConsBadOptionError AddOption( '--compiler', dest='compiler', action='store', default='gcc', type='string', ) # ... other SConscript logic ... try: ValidateOptions(throw_exception=True) except SConsBadOptionError as e: print(f"ValidateOptions detects a fail: ", e.opt_str) Exit(3)
New in version 4.5.0
Value
(value, [built_value], [name]
), env
.Value
(value, [built_value], [name]
)
Returns a Node object representing the specified Python
value
.
Value Nodes can be used as dependencies of targets.
If the string representation of the Value Node
changes between SCons runs, it is considered
out of date and any targets depending it will be rebuilt.
Since Value Nodes have no filesystem representation,
timestamps are not used; the timestamp deciders
perform the same content-based up to date check.
The optional
built_value
argument can be specified
when the Value Node is created
to indicate the Node should already be considered "built."
The optional name
parameter can be provided as an
alternative name for the resulting Value
node;
this is advised if the value
parameter
cannot be converted to a string.
Value Nodes have a
write
method that can be used to "build" a Value Node
by setting a new value.
The corresponding
read
method returns the built value of the Node.
Changed in version 4.0:
the name
parameter was added.
Examples:
env = Environment() def create(target, source, env): """Action function to create a file from a Value. Writes 'prefix=$SOURCE' into the file name given as $TARGET. """ with open(str(target[0]), 'wb') as f: f.write(b'prefix=' + source[0].get_contents() + b'\n') # Fetch the prefix= argument, if any, from the command line. # Use /usr/local as the default. prefix = ARGUMENTS.get('prefix', '/usr/local') # Attach builder named Config to the construction environment # using the 'create' action function above. env['BUILDERS']['Config'] = Builder(action=create) env.Config(target='package-config', source=Value(prefix)) def build_value(target, source, env): """Action function to "build" a Value. Writes contents of $SOURCE into $TARGET, thus updating if it existed. """ target[0].write(source[0].get_contents()) output = env.Value('before') input = env.Value('after') # Attach a builder named UpdateValue to the construction environment # using the 'build_value' action function above. env['BUILDERS']['UpdateValue'] = Builder(action=build_value) env.UpdateValue(target=Value(output), source=Value(input))
VariantDir
(variant_dir, src_dir, [duplicate]
), env
.VariantDir
(variant_dir, src_dir, [duplicate]
)
Sets up a mapping to define a variant build directory in
variant_dir
.
src_dir
must not be underneath
variant_dir
.
A VariantDir
mapping is global, even if called using the
env.VariantDir
form.
VariantDir
can be called multiple times with the same
src_dir
to set up multiple variant builds with different options.
Note if variant_dir
is not under the project top directory,
target selection rules will not pick targets in the
variant directory unless they are explicitly specified.
When files in variant_dir
are referenced,
SCons backfills as needed with files from src_dir
to create a complete build directory.
By default, SCons
physically duplicates the source files, SConscript files,
and directory structure as needed into the variant directory.
Thus, a build performed in the variant directory is guaranteed to be identical
to a build performed in the source directory even if
intermediate source files are generated during the build,
or if preprocessors or other scanners search for included files
using paths 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 duplicating,
and is safe for most builds;
revert to duplicate=True
if it causes problems.
VariantDir
works most naturally when used with a subsidiary SConscript file.
The subsidiary SConscript file must be called as if it were in
variant_dir
,
regardless of the value of
duplicate
.
When calling an SConscript file, you can use the
exports
keyword argument
to pass parameters (individually or as an appropriately set up environment)
so the SConscript can pick up the right settings for that variant build.
The SConscript must Import
these to use them. Example:
env1 = Environment(...settings for variant1...) env2 = Environment(...settings for variant2...) # run src/SConscript in two variant directories VariantDir('build/variant1', 'src') SConscript('build/variant1/SConscript', exports={"env": env1}) VariantDir('build/variant2', 'src') SConscript('build/variant2/SConscript', exports={"env": env2})
See also the
SConscript
function
for another way to specify a variant directory
in conjunction with calling a subsidiary SConscript file.
More 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)
WhereIs
(program, [path, pathext, reject]
), env
.WhereIs
(program, [path, pathext, reject]
)
Searches for the specified executable
program
,
returning the full path to the program
or None
.
When called as a construction environment method,
searches the paths in the
path
keyword argument,
or if None
(the default)
the paths listed in the construction environment
(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 construction environment
(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.