How to use SCons - 10 common examples

If a Node for the specified "p" doesn't already exist, and
        "create" is specified, the Node may be created after recursive
        invocation to find or create the parent directory or directories.
        """
        k = _my_normcase(p)
        try:
            result = self._lookupDict[k]
        except KeyError:
            if not create:
                msg = "No such file or directory: '%s' in '%s' (and create is False)" % (p, str(self))
                raise SCons.Errors.UserError(msg)
            # There is no Node for this path name, and we're allowed
            # to create it.
            dir_name, file_name = p.rsplit('/',1)
            dir_node = self._lookup_abs(dir_name, Dir)
            result = klass(file_name, dir_node, self.fs)

            # Double-check on disk (as configured) that the Node we
            # created matches whatever is out there in the real world.
            result.diskcheck_match()

            self._lookupDict[k] = result
            dir_node.entries[_my_normcase(file_name)] = result
            dir_node.implicit = None
        else:
            # There is already a Node for this path name.  Allow it to
            # complain if we were looking for an inappropriate type.
            result.must_be_same(klass)
        return result

If a Node for the specified "p" doesn't already exist, and
        "create" is specified, the Node may be created after recursive
        invocation to find or create the parent directory or directories.
        """
        k = _my_normcase(p)
        try:
            result = self._lookupDict[k]
        except KeyError:
            if not create:
                msg = "No such file or directory: '%s' in '%s' (and create is False)" % (p, str(self))
                raise SCons.Errors.UserError(msg)
            # There is no Node for this path name, and we're allowed
            # to create it.
            dir_name, file_name = p.rsplit('/',1)
            dir_node = self._lookup_abs(dir_name, Dir)
            result = klass(file_name, dir_node, self.fs)

            # Double-check on disk (as configured) that the Node we
            # created matches whatever is out there in the real world.
            result.diskcheck_match()

            self._lookupDict[k] = result
            dir_node.entries[_my_normcase(file_name)] = result
            dir_node.implicit = None
        else:
            # There is already a Node for this path name.  Allow it to
            # complain if we were looking for an inappropriate type.
            result.must_be_same(klass)
        return result

fd = self.default_filedir
        dir, name = os.path.split(fd)
        drive, d = _my_splitdrive(dir)
        if not name and d[:1] in ('/', OS_SEP):
            #return p.fs.get_root(drive).dir_on_disk(name)
            return p.fs.get_root(drive)
        if dir:
            p = self.filedir_lookup(p, dir)
            if not p:
                return None
        norm_name = _my_normcase(name)
        try:
            node = p.entries[norm_name]
        except KeyError:
            return p.dir_on_disk(name)
        if isinstance(node, Dir):
            return node
        if isinstance(node, Entry):
            node.must_be_same(Dir)
            return node
        return None

def _demo_windows():
    #
    # Example 1: Connecting several subprocesses
    #
    print "Looking for 'PROMPT' in set output..."
    p1 = Popen("set", stdout=PIPE, shell=True)
    p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE)
    print repr(p2.communicate()[0])

    #
    # Example 2: Simple execution of program
    #
    print "Executing calc..."
    p = Popen("calc")
    p.wait()

def _demo_windows():
    #
    # Example 1: Connecting several subprocesses
    #
    print "Looking for 'PROMPT' in set output..."
    p1 = Popen("set", stdout=PIPE, shell=True)
    p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE)
    print repr(p2.communicate()[0])

    #
    # Example 2: Simple execution of program
    #
    print "Executing calc..."
    p = Popen("calc")
    p.wait()

plist = Popen(["ps"], stdout=PIPE).communicate()[0]
    print "Process list:"
    print plist

    #
    # Example 2: Change uid before executing child
    #
    if os.getuid() == 0:
        p = Popen(["id"], preexec_fn=lambda: os.setuid(100))
        p.wait()

    #
    # Example 3: Connecting several subprocesses
    #
    print "Looking for 'hda'..."
    p1 = Popen(["dmesg"], stdout=PIPE)
    p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
    print repr(p2.communicate()[0])

    #
    # Example 4: Catch execution error
    #
    print
    print "Trying a weird file..."
    try:
        print Popen(["/this/path/does/not/exist"]).communicate()
    except OSError, e:
        if e.errno == errno.ENOENT:
            print "The file didn't exist.  I thought so..."
            print "Child traceback:"
            print e.child_traceback
        else:

def _demo_posix():
    #
    # Example 1: Simple redirection: Get process list
    #
    plist = Popen(["ps"], stdout=PIPE).communicate()[0]
    print "Process list:"
    print plist

    #
    # Example 2: Change uid before executing child
    #
    if os.getuid() == 0:
        p = Popen(["id"], preexec_fn=lambda: os.setuid(100))
        p.wait()

    #
    # Example 3: Connecting several subprocesses
    #
    print "Looking for 'hda'..."
    p1 = Popen(["dmesg"], stdout=PIPE)
    p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)

print "Process list:"
    print plist

    #
    # Example 2: Change uid before executing child
    #
    if os.getuid() == 0:
        p = Popen(["id"], preexec_fn=lambda: os.setuid(100))
        p.wait()

    #
    # Example 3: Connecting several subprocesses
    #
    print "Looking for 'hda'..."
    p1 = Popen(["dmesg"], stdout=PIPE)
    p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
    print repr(p2.communicate()[0])

    #
    # Example 4: Catch execution error
    #
    print
    print "Trying a weird file..."
    try:
        print Popen(["/this/path/does/not/exist"]).communicate()
    except OSError, e:
        if e.errno == errno.ENOENT:
            print "The file didn't exist.  I thought so..."
            print "Child traceback:"
            print e.child_traceback
        else:
            print "Error", e.errno

def _demo_windows():
    #
    # Example 1: Connecting several subprocesses
    #
    print "Looking for 'PROMPT' in set output..."
    p1 = Popen("set", stdout=PIPE, shell=True)
    p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE)
    print repr(p2.communicate()[0])

    #
    # Example 2: Simple execution of program
    #
    print "Executing calc..."
    p = Popen("calc")
    p.wait()

if isinstance(act, ActionBase):
        return act

    if is_String(act):
        var=SCons.Util.get_environment_var(act)
        if var:
            # This looks like a string that is purely an Environment
            # variable reference, like "$FOO" or "${FOO}".  We do
            # something special here...we lazily evaluate the contents
            # of that Environment variable, so a user could put something
            # like a function or a CommandGenerator in that variable
            # instead of a string.
            return LazyAction(var, kw)
        commands = str(act).split('\n')
        if len(commands) == 1:
            return CommandAction(commands[0], **kw)
        # The list of string commands may include a LazyAction, so we
        # reprocess them via _do_create_list_action.
        return _do_create_list_action(commands, kw)
    
    if is_List(act):
        return CommandAction(act, **kw)

    if callable(act):
        try:
            gen = kw['generator']
            del kw['generator']
        except KeyError:
            gen = 0
        if gen:
            action_type = CommandGeneratorAction
        else: