spawn.py

"""distutils.spawn

Provides the 'spawn()' function, a front-end to various platform-
specific functions for launching another program in a sub-process.
Also provides the 'find_executable()' to search the path for a given
executable name.
"""

importsys
importos

fromdistutils.errorsimportDistutilsPlatformError, DistutilsExecError
fromdistutils.debugimportDEBUG
fromdistutilsimportlog

defspawn(cmd, search_path=1, verbose=0, dry_run=0):
"""Run another program, specified as a command list 'cmd', in a new process.

 'cmd' is just the argument list for the new process, ie.
 cmd[0] is the program to run and cmd[1:] are the rest of its arguments.
 There is no way to run a program with a name different from that of its
 executable.

 If 'search_path' is true (the default), the system's executable
 search path will be used to find the program; otherwise, cmd[0]
 must be the exact path to the executable. If 'dry_run' is true,
 the command will not actually be run.

 Raise DistutilsExecError if running the program fails in any way; just
 return on success.
 """
# cmd is documented as a list, but just in case some code passes a tuple
# in, protect our %-formatting code against horrible death
cmd=list(cmd)
ifos.name=='posix':
_spawn_posix(cmd, search_path, dry_run=dry_run)
elifos.name=='nt':
_spawn_nt(cmd, search_path, dry_run=dry_run)
else:
raiseDistutilsPlatformError(
"don't know how to spawn programs on platform '%s'"%os.name)

def_nt_quote_args(args):
"""Quote command-line arguments for DOS/Windows conventions.

 Just wraps every argument which contains blanks in double quotes, and
 returns a new argument list.
 """
# XXX this doesn't seem very robust to me -- but if the Windows guys
# say it'll work, I guess I'll have to accept it. (What if an arg
# contains quotes? What other magic characters, other than spaces,
# have to be escaped? Is there an escaping mechanism other than
# quoting?)
fori, arginenumerate(args):
if' 'inarg:
args[i] ='"%s"'%arg
returnargs

def_spawn_nt(cmd, search_path=1, verbose=0, dry_run=0):
executable=cmd[0]
cmd=_nt_quote_args(cmd)
ifsearch_path:
# either we find one or it stays the same
executable=find_executable(executable) orexecutable
log.info(' '.join([executable] +cmd[1:]))
ifnotdry_run:
# spawn for NT requires a full path to the .exe
try:
rc=os.spawnv(os.P_WAIT, executable, cmd)
exceptOSErrorasexc:
# this seems to happen when the command isn't found
ifnotDEBUG:
cmd=executable
raiseDistutilsExecError(
"command %r failed: %s"% (cmd, exc.args[-1]))
ifrc!=0:
# and this reflects the command running but failing
ifnotDEBUG:
cmd=executable
raiseDistutilsExecError(
"command %r failed with exit status %d"% (cmd, rc))

ifsys.platform=='darwin':
fromdistutilsimportsysconfig
_cfg_target=None
_cfg_target_split=None

def_spawn_posix(cmd, search_path=1, verbose=0, dry_run=0):
log.info(' '.join(cmd))
ifdry_run:
return
executable=cmd[0]
exec_fn=search_pathandos.execvporos.execv
env=None
ifsys.platform=='darwin':
global_cfg_target, _cfg_target_split
if_cfg_targetisNone:
_cfg_target=sysconfig.get_config_var(
'MACOSX_DEPLOYMENT_TARGET') or''
if_cfg_target:
_cfg_target_split= [int(x) forxin_cfg_target.split('.')]
if_cfg_target:
# ensure that the deployment target of build process is not less
# than that used when the interpreter was built. This ensures
# extension modules are built with correct compatibility values
cur_target=os.environ.get('MACOSX_DEPLOYMENT_TARGET', _cfg_target)
if_cfg_target_split> [int(x) forxincur_target.split('.')]:
my_msg= ('$MACOSX_DEPLOYMENT_TARGET mismatch: '
'now "%s" but "%s" during configure'
% (cur_target, _cfg_target))
raiseDistutilsPlatformError(my_msg)
env=dict(os.environ,
MACOSX_DEPLOYMENT_TARGET=cur_target)
exec_fn=search_pathandos.execvpeoros.execve
pid=os.fork()
ifpid==0: # in the child
try:
ifenvisNone:
exec_fn(executable, cmd)
else:
exec_fn(executable, cmd, env)
exceptOSErrorase:
ifnotDEBUG:
cmd=executable
sys.stderr.write("unable to execute %r: %s\n"
% (cmd, e.strerror))
os._exit(1)

ifnotDEBUG:
cmd=executable
sys.stderr.write("unable to execute %r for unknown reasons"%cmd)
os._exit(1)
else: # in the parent
# Loop until the child either exits or is terminated by a signal
# (ie. keep waiting if it's merely stopped)
whileTrue:
try:
pid, status=os.waitpid(pid, 0)
exceptOSErrorasexc:
ifnotDEBUG:
cmd=executable
raiseDistutilsExecError(
"command %r failed: %s"% (cmd, exc.args[-1]))
ifos.WIFSIGNALED(status):
ifnotDEBUG:
cmd=executable
raiseDistutilsExecError(
"command %r terminated by signal %d"
% (cmd, os.WTERMSIG(status)))
elifos.WIFEXITED(status):
exit_status=os.WEXITSTATUS(status)
ifexit_status==0:
return# hey, it succeeded!
else:
ifnotDEBUG:
cmd=executable
raiseDistutilsExecError(
"command %r failed with exit status %d"
% (cmd, exit_status))
elifos.WIFSTOPPED(status):
continue
else:
ifnotDEBUG:
cmd=executable
raiseDistutilsExecError(
"unknown error executing %r: termination status %d"
% (cmd, status))

deffind_executable(executable, path=None):
"""Tries to find 'executable' in the directories listed in 'path'.

 A string listing directories separated by 'os.pathsep'; defaults to
 os.environ['PATH']. Returns the complete filename or None if not found.
 """
_, ext=os.path.splitext(executable)
if (sys.platform=='win32') and (ext!='.exe'):
executable=executable+'.exe'

ifos.path.isfile(executable):
returnexecutable

ifpathisNone:
path=os.environ.get('PATH', None)
ifpathisNone:
try:
path=os.confstr("CS_PATH")
except (AttributeError, ValueError):
# os.confstr() or CS_PATH is not available
path=os.defpath
# bpo-35755: Don't use os.defpath if the PATH environment variable is
# set to an empty string

# PATH='' doesn't match, whereas PATH=':' looks in the current directory
ifnotpath:
returnNone

paths=path.split(os.pathsep)
forpinpaths:
f=os.path.join(p, executable)
ifos.path.isfile(f):
# the file exists, we have a shot at spawn working
returnf
returnNone