"""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.
"""

# This module should be kept compatible with Python 2.1.

__revision__ = "$Id: spawn.py 37828 2004-11-10 22:23:15Z loewis $"

import sys, os, string
from distutils.errors import *
from distutils import log

def spawn (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.
"""
if os.name == 'posix':
_spawn_posix(cmd, search_path, dry_run=dry_run)
elif os.name == 'nt':
_spawn_nt(cmd, search_path, dry_run=dry_run)
elif os.name == 'os2':
_spawn_os2(cmd, search_path, dry_run=dry_run)
else:
raise DistutilsPlatformError, \
"don't know how to spawn programs on platform '%s'" % os.name

# spawn ()


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?)

for i in range(len(args)):
if string.find(args[i], ' ') != -1:
args[i] = '"%s"' % args[i]
return args

def _spawn_nt (cmd,
search_path=1,
verbose=0,
dry_run=0):

executable = cmd[0]
cmd = _nt_quote_args(cmd)
if search_path:
# either we find one or it stays the same
executable = find_executable(executable) or executable
log.info(string.join([executable] + cmd[1:], ' '))
if not dry_run:
# spawn for NT requires a full path to the .exe
try:
rc = os.spawnv(os.P_WAIT, executable, cmd)
except OSError, exc:
# this seems to happen when the command isn't found
raise DistutilsExecError, \
"command '%s' failed: %s" % (cmd[0], exc[-1])
if rc != 0:
# and this reflects the command running but failing
raise DistutilsExecError, \
"command '%s' failed with exit status %d" % (cmd[0], rc)


def _spawn_os2 (cmd,
search_path=1,
verbose=0,
dry_run=0):

executable = cmd[0]
#cmd = _nt_quote_args(cmd)
if search_path:
# either we find one or it stays the same
executable = find_executable(executable) or executable
log.info(string.join([executable] + cmd[1:], ' '))
if not dry_run:
# spawnv for OS/2 EMX requires a full path to the .exe
try:
rc = os.spawnv(os.P_WAIT, executable, cmd)
except OSError, exc:
# this seems to happen when the command isn't found
raise DistutilsExecError, \
"command '%s' failed: %s" % (cmd[0], exc[-1])
if rc != 0:
# and this reflects the command running but failing
print "command '%s' failed with exit status %d" % (cmd[0], rc)
raise DistutilsExecError, \
"command '%s' failed with exit status %d" % (cmd[0], rc)


def _spawn_posix (cmd,
search_path=1,
verbose=0,
dry_run=0):

log.info(string.join(cmd, ' '))
if dry_run:
return
exec_fn = search_path and os.execvp or os.execv

pid = os.fork()

if pid == 0: # in the child
try:
#print "cmd[0] =", cmd[0]
#print "cmd =", cmd
exec_fn(cmd[0], cmd)
except OSError, e:
sys.stderr.write("unable to execute %s: %s\n" %
(cmd[0], e.strerror))
os._exit(1)

sys.stderr.write("unable to execute %s for unknown reasons" % cmd[0])
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)
while 1:
try:
(pid, status) = os.waitpid(pid, 0)
except OSError, exc:
import errno
if exc.errno == errno.EINTR:
continue
raise DistutilsExecError, \
"command '%s' failed: %s" % (cmd[0], exc[-1])
if os.WIFSIGNALED(status):
raise DistutilsExecError, \
"command '%s' terminated by signal %d" % \
(cmd[0], os.WTERMSIG(status))

elif os.WIFEXITED(status):
exit_status = os.WEXITSTATUS(status)
if exit_status == 0:
return # hey, it succeeded!
else:
raise DistutilsExecError, \
"command '%s' failed with exit status %d" % \
(cmd[0], exit_status)

elif os.WIFSTOPPED(status):
continue

else:
raise DistutilsExecError, \
"unknown error executing '%s': termination status %d" % \
(cmd[0], status)
# _spawn_posix ()


def find_executable(executable, path=None):
"""Try 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.
"""
if path is None:
path = os.environ['PATH']
paths = string.split(path, os.pathsep)
(base, ext) = os.path.splitext(executable)
if (sys.platform == 'win32' or os.name == 'os2') and (ext != '.exe'):
executable = executable + '.exe'
if not os.path.isfile(executable):
for p in paths:
f = os.path.join(p, executable)
if os.path.isfile(f):
# the file exists, we have a shot at spawn working
return f
return None
else:
return executable

# find_executable()