spawn.py revision be19ed77ddb047e02fe94d142181062af6d99dcc 
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__ = "$Id$"
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 as 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 as 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 as 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 as 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()
202