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/Lib/distutils/spawn.py

http://unladen-swallow.googlecode.com/
Python | 201 lines | 197 code | 1 blank | 3 comment | 4 complexity | 2d81e0f5edcaf80bf1cbdf57b4acb8fd MD5 | raw file
  1"""distutils.spawn
  2
  3Provides the 'spawn()' function, a front-end to various platform-
  4specific functions for launching another program in a sub-process.
  5Also provides the 'find_executable()' to search the path for a given
  6executable name.
  7"""
  8
  9# This module should be kept compatible with Python 2.1.
 10
 11__revision__ = "$Id: spawn.py 37828 2004-11-10 22:23:15Z loewis $"
 12
 13import sys, os, string
 14from distutils.errors import *
 15from distutils import log
 16
 17def spawn (cmd,
 18           search_path=1,
 19           verbose=0,
 20           dry_run=0):
 21
 22    """Run another program, specified as a command list 'cmd', in a new
 23    process.  'cmd' is just the argument list for the new process, ie.
 24    cmd[0] is the program to run and cmd[1:] are the rest of its arguments.
 25    There is no way to run a program with a name different from that of its
 26    executable.
 27
 28    If 'search_path' is true (the default), the system's executable
 29    search path will be used to find the program; otherwise, cmd[0]
 30    must be the exact path to the executable.  If 'dry_run' is true,
 31    the command will not actually be run.
 32
 33    Raise DistutilsExecError if running the program fails in any way; just
 34    return on success.
 35    """
 36    if os.name == 'posix':
 37        _spawn_posix(cmd, search_path, dry_run=dry_run)
 38    elif os.name == 'nt':
 39        _spawn_nt(cmd, search_path, dry_run=dry_run)
 40    elif os.name == 'os2':
 41        _spawn_os2(cmd, search_path, dry_run=dry_run)
 42    else:
 43        raise DistutilsPlatformError, \
 44              "don't know how to spawn programs on platform '%s'" % os.name
 45
 46# spawn ()
 47
 48
 49def _nt_quote_args (args):
 50    """Quote command-line arguments for DOS/Windows conventions: just
 51    wraps every argument which contains blanks in double quotes, and
 52    returns a new argument list.
 53    """
 54
 55    # XXX this doesn't seem very robust to me -- but if the Windows guys
 56    # say it'll work, I guess I'll have to accept it.  (What if an arg
 57    # contains quotes?  What other magic characters, other than spaces,
 58    # have to be escaped?  Is there an escaping mechanism other than
 59    # quoting?)
 60
 61    for i in range(len(args)):
 62        if string.find(args[i], ' ') != -1:
 63            args[i] = '"%s"' % args[i]
 64    return args
 65
 66def _spawn_nt (cmd,
 67               search_path=1,
 68               verbose=0,
 69               dry_run=0):
 70
 71    executable = cmd[0]
 72    cmd = _nt_quote_args(cmd)
 73    if search_path:
 74        # either we find one or it stays the same
 75        executable = find_executable(executable) or executable
 76    log.info(string.join([executable] + cmd[1:], ' '))
 77    if not dry_run:
 78        # spawn for NT requires a full path to the .exe
 79        try:
 80            rc = os.spawnv(os.P_WAIT, executable, cmd)
 81        except OSError, exc:
 82            # this seems to happen when the command isn't found
 83            raise DistutilsExecError, \
 84                  "command '%s' failed: %s" % (cmd[0], exc[-1])
 85        if rc != 0:
 86            # and this reflects the command running but failing
 87            raise DistutilsExecError, \
 88                  "command '%s' failed with exit status %d" % (cmd[0], rc)
 89
 90
 91def _spawn_os2 (cmd,
 92                search_path=1,
 93                verbose=0,
 94                dry_run=0):
 95
 96    executable = cmd[0]
 97    #cmd = _nt_quote_args(cmd)
 98    if search_path:
 99        # either we find one or it stays the same
100        executable = find_executable(executable) or executable
101    log.info(string.join([executable] + cmd[1:], ' '))
102    if not dry_run:
103        # spawnv for OS/2 EMX requires a full path to the .exe
104        try:
105            rc = os.spawnv(os.P_WAIT, executable, cmd)
106        except OSError, exc:
107            # this seems to happen when the command isn't found
108            raise DistutilsExecError, \
109                  "command '%s' failed: %s" % (cmd[0], exc[-1])
110        if rc != 0:
111            # and this reflects the command running but failing
112            print "command '%s' failed with exit status %d" % (cmd[0], rc)
113            raise DistutilsExecError, \
114                  "command '%s' failed with exit status %d" % (cmd[0], rc)
115
116
117def _spawn_posix (cmd,
118                  search_path=1,
119                  verbose=0,
120                  dry_run=0):
121
122    log.info(string.join(cmd, ' '))
123    if dry_run:
124        return
125    exec_fn = search_path and os.execvp or os.execv
126
127    pid = os.fork()
128
129    if pid == 0:                        # in the child
130        try:
131            #print "cmd[0] =", cmd[0]
132            #print "cmd =", cmd
133            exec_fn(cmd[0], cmd)
134        except OSError, e:
135            sys.stderr.write("unable to execute %s: %s\n" %
136                             (cmd[0], e.strerror))
137            os._exit(1)
138
139        sys.stderr.write("unable to execute %s for unknown reasons" % cmd[0])
140        os._exit(1)
141
142
143    else:                               # in the parent
144        # Loop until the child either exits or is terminated by a signal
145        # (ie. keep waiting if it's merely stopped)
146        while 1:
147            try:
148                (pid, status) = os.waitpid(pid, 0)
149            except OSError, exc:
150                import errno
151                if exc.errno == errno.EINTR:
152                    continue
153                raise DistutilsExecError, \
154                      "command '%s' failed: %s" % (cmd[0], exc[-1])
155            if os.WIFSIGNALED(status):
156                raise DistutilsExecError, \
157                      "command '%s' terminated by signal %d" % \
158                      (cmd[0], os.WTERMSIG(status))
159
160            elif os.WIFEXITED(status):
161                exit_status = os.WEXITSTATUS(status)
162                if exit_status == 0:
163                    return              # hey, it succeeded!
164                else:
165                    raise DistutilsExecError, \
166                          "command '%s' failed with exit status %d" % \
167                          (cmd[0], exit_status)
168
169            elif os.WIFSTOPPED(status):
170                continue
171
172            else:
173                raise DistutilsExecError, \
174                      "unknown error executing '%s': termination status %d" % \
175                      (cmd[0], status)
176# _spawn_posix ()
177
178
179def find_executable(executable, path=None):
180    """Try to find 'executable' in the directories listed in 'path' (a
181    string listing directories separated by 'os.pathsep'; defaults to
182    os.environ['PATH']).  Returns the complete filename or None if not
183    found.
184    """
185    if path is None:
186        path = os.environ['PATH']
187    paths = string.split(path, os.pathsep)
188    (base, ext) = os.path.splitext(executable)
189    if (sys.platform == 'win32' or os.name == 'os2') and (ext != '.exe'):
190        executable = executable + '.exe'
191    if not os.path.isfile(executable):
192        for p in paths:
193            f = os.path.join(p, executable)
194            if os.path.isfile(f):
195                # the file exists, we have a shot at spawn working
196                return f
197        return None
198    else:
199        return executable
200
201# find_executable()