Module to spawn sub-commands in a platform-independent way.

Initial revision only includes support for POSIX-style fork-and-exec.

Lib/distutils/spawn.py

@@ -0,0 +1,106 @@
+"""distutils.spawn
+
+Provides the 'spawn()' function, a front-end to various platform-
+specific functions for launching another program in a sub-process."""
+
+# created 1999/07/24, Greg Ward
+
+__rcsid__ = "$Id$"
+
+import sys, os, string
+from distutils.errors import *
+
+
+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 'verbose' is true, a
+       one-line summary of the command will be printed before it is run.
+       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, verbose, dry_run)
+    elif os.name == 'windows':          # ???
+        # XXX should 'args' be cmd[1:] or cmd?
+        # XXX how do we detect failure?
+        # XXX how to do this in pre-1.5.2?
+        # XXX is P_WAIT the correct mode?
+        # XXX how to make Windows search the path?
+        if verbose:
+            print string.join (cmd, ' ')
+        if not dry_run:
+            os.spawnv (os.P_WAIT, cmd[0], cmd[1:])
+    else:
+        raise DistutilsPlatformError, \
+              "don't know how to spawn programs on platform '%s'" % os.name
+
+# spawn ()
+
+
+def _spawn_posix (cmd,
+                  search_path=1,
+                  verbose=0,
+                  dry_run=0):
+
+    if verbose:
+        print 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:
+            (pid, status) = os.waitpid (pid, 0)
+            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 ()