Lib/distutils/spawn.py

   1 """distutils.spawn
   2
   3 Provides the 'spawn()' function, a front-end to various platform-
   4 specific functions for launching another program in a sub-process."""
   5
   6 # created 1999/07/24, Greg Ward
   7
   8 __revision__ = "$Id$"
   9
  10 import sys, os, string
  11 from distutils.errors import *
  12
  13
  14 def spawn (cmd,
  15            search_path=1,
  16            verbose=0,
  17            dry_run=0):
  18
  19     """Run another program, specified as a command list 'cmd', in a new
  20        process.  'cmd' is just the argument list for the new process, ie.
  21        cmd[0] is the program to run and cmd[1:] are the rest of its
  22        arguments.  There is no way to run a program with a name different
  23        from that of its executable.
  24
  25        If 'search_path' is true (the default), the system's executable
  26        search path will be used to find the program; otherwise, cmd[0] must
  27        be the exact path to the executable.  If 'verbose' is true, a
  28        one-line summary of the command will be printed before it is run.
  29        If 'dry_run' is true, the command will not actually be run.
  30
  31        Raise DistutilsExecError if running the program fails in any way;
  32        just return on success."""
  33
  34     if os.name == 'posix':
  35         _spawn_posix (cmd, search_path, verbose, dry_run)
  36     elif os.name == 'nt':
  37         _spawn_nt (cmd, search_path, verbose, dry_run)
  38     else:
  39         raise DistutilsPlatformError, \
  40               "don't know how to spawn programs on platform '%s'" % os.name
  41
  42 # spawn ()
  43
  44
  45 def _nt_quote_args (args):
  46     """Obscure quoting command line arguments on NT.
  47        Simply quote every argument which contains blanks."""
  48
  49     # XXX this doesn't seem very robust to me -- but if the Windows guys
  50     # say it'll work, I guess I'll have to accept it.  (What if an arg
  51     # contains quotes?  What other magic characters, other than spaces,
  52     # have to be escaped?  Is there an escaping mechanism other than
  53     # quoting?)
  54
  55     for i in range (len (args)):
  56         if string.find (args[i], ' ') != -1:
  57             args[i] = '"%s"' % args[i]
  58     return args
  59
  60 def _spawn_nt (cmd,
  61                search_path=1,
  62                verbose=0,
  63                dry_run=0):
  64
  65     executable = cmd[0]
  66     cmd = _nt_quote_args (cmd)
  67     if search_path:
  68         paths = string.split( os.environ['PATH'], os.pathsep)
  69         base,ext = os.path.splitext(executable)
  70         if (ext != '.exe'):
  71             executable = executable + '.exe'
  72         if not os.path.isfile(executable):
  73             paths.reverse()         # go over the paths and keep the last one
  74             for p in paths:
  75                 f = os.path.join( p, executable )
  76                 if os.path.isfile ( f ):
  77                     # the file exists, we have a shot at spawn working
  78                     executable = f
  79     if verbose:
  80         print string.join ([executable] + cmd[1:], ' ')
  81     if not dry_run:
  82         # spawn for NT requires a full path to the .exe
  83         try:
  84             rc = os.spawnv (os.P_WAIT, executable, cmd)
  85         except OSError, exc:
  86             # this seems to happen when the command isn't found
  87             raise DistutilsExecError, \
  88                   "command '%s' failed: %s" % (cmd[0], exc[-1])
  89         if rc != 0:
  90             # and this reflects the command running but failing
  91             raise DistutilsExecError, \
  92                   "command '%s' failed with exit status %d" % (cmd[0], rc)
  93
  94
  95
  96 def _spawn_posix (cmd,
  97                   search_path=1,
  98                   verbose=0,
  99                   dry_run=0):
 100
 101     if verbose:
 102         print string.join (cmd, ' ')
 103     if dry_run:
 104         return
 105     exec_fn = search_path and os.execvp or os.execv
 106
 107     pid = os.fork ()
 108
 109     if pid == 0:                        # in the child
 110         try:
 111             #print "cmd[0] =", cmd[0]
 112             #print "cmd =", cmd
 113             exec_fn (cmd[0], cmd)
 114         except OSError, e:
 115             sys.stderr.write ("unable to execute %s: %s\n" %
 116                               (cmd[0], e.strerror))
 117             os._exit (1)
 118
 119         sys.stderr.write ("unable to execute %s for unknown reasons" % cmd[0])
 120         os._exit (1)
 121
 122
 123     else:                               # in the parent
 124         # Loop until the child either exits or is terminated by a signal
 125         # (ie. keep waiting if it's merely stopped)
 126         while 1:
 127             (pid, status) = os.waitpid (pid, 0)
 128             if os.WIFSIGNALED (status):
 129                 raise DistutilsExecError, \
 130                       "command '%s' terminated by signal %d" % \
 131                       (cmd[0], os.WTERMSIG (status))
 132
 133             elif os.WIFEXITED (status):
 134                 exit_status = os.WEXITSTATUS (status)
 135                 if exit_status == 0:
 136                     return              # hey, it succeeded!
 137                 else:
 138                     raise DistutilsExecError, \
 139                           "command '%s' failed with exit status %d" % \
 140                           (cmd[0], exit_status)
 141
 142             elif os.WIFSTOPPED (status):
 143                 continue
 144
 145             else:
 146                 raise DistutilsExecError, \
 147                       "unknown error executing '%s': termination status %d" % \
 148                       (cmd[0], status)
 149 # _spawn_posix ()