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 __rcsid__ = "$Id$"
   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 _spawn_nt ( cmd,
  46                 search_path=1,
  47                 verbose=0,
  48                 dry_run=0):
  49     executable = cmd[0]
  50     if search_path:
  51         paths = string.split( os.environ['PATH'], os.pathsep)
  52         base,ext = os.path.splitext(executable)
  53         if (ext != '.exe'):
  54             executable = executable + '.exe'
  55         if not os.path.isfile(executable):
  56             paths.reverse()         # go over the paths and keep the last one
  57             for p in paths:
  58                 f = os.path.join( p, executable )
  59                 if os.path.isfile ( f ):
  60                     # the file exists, we have a shot at spawn working
  61                     executable = f
  62     if verbose:
  63         print string.join ( [executable] + cmd[1:], ' ')
  64     if not dry_run:
  65         # spawn for NT requires a full path to the .exe
  66         try:
  67             rc = os.spawnv (os.P_WAIT, executable, cmd)
  68         except OSError, exc:
  69             # this seems to happen when the command isn't found
  70             raise DistutilsExecError, \
  71                   "command '%s' failed: %s" % (cmd[0], exc[-1])
  72         if rc != 0:
  73             # and this reflects the command running but failing
  74             raise DistutilsExecError, \
  75                   "command '%s' failed with exit status %d" % (cmd[0], rc)
  76
  77
  78
  79 def _spawn_posix (cmd,
  80                   search_path=1,
  81                   verbose=0,
  82                   dry_run=0):
  83
  84     if verbose:
  85         print string.join (cmd, ' ')
  86     if dry_run:
  87         return
  88     exec_fn = search_path and os.execvp or os.execv
  89
  90     pid = os.fork ()
  91
  92     if pid == 0:                        # in the child
  93         try:
  94             #print "cmd[0] =", cmd[0]
  95             #print "cmd =", cmd
  96             exec_fn (cmd[0], cmd)
  97         except OSError, e:
  98             sys.stderr.write ("unable to execute %s: %s\n" %
  99                               (cmd[0], e.strerror))
 100             os._exit (1)
 101
 102         sys.stderr.write ("unable to execute %s for unknown reasons" % cmd[0])
 103         os._exit (1)
 104
 105
 106     else:                               # in the parent
 107         # Loop until the child either exits or is terminated by a signal
 108         # (ie. keep waiting if it's merely stopped)
 109         while 1:
 110             (pid, status) = os.waitpid (pid, 0)
 111             if os.WIFSIGNALED (status):
 112                 raise DistutilsExecError, \
 113                       "command '%s' terminated by signal %d" % \
 114                       (cmd[0], os.WTERMSIG (status))
 115
 116             elif os.WIFEXITED (status):
 117                 exit_status = os.WEXITSTATUS (status)
 118                 if exit_status == 0:
 119                     return              # hey, it succeeded!
 120                 else:
 121                     raise DistutilsExecError, \
 122                           "command '%s' failed with exit status %d" % \
 123                           (cmd[0], exit_status)
 124
 125             elif os.WIFSTOPPED (status):
 126                 continue
 127
 128             else:
 129                 raise DistutilsExecError, \
 130                       "unknown error executing '%s': termination status %d" % \
 131                       (cmd[0], status)
 132 # _spawn_posix ()