ia64/xen-unstable

view tools/python/xen/util/xpopen.py @ 5118:242591aabc7a

bitkeeper revision 1.1528 (4292fdfc5zZkxl3RcxrdBZCU6Rd8EA)

XendDomain.py:
Handle error case where exec fails.
xpopen.py:
Exit with 127 if exec fails.
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
author cl349@firebug.cl.cam.ac.uk
date Tue May 24 10:12:12 2005 +0000 (2005-05-24)
parents 6c5699e95a56
children 734ebf0aa35f dd3849d6cdea
line source
1 #
2 # Copyright (c) 2001, 2002, 2003, 2004 Python Software Foundation; All Rights Reserved
3 #
4 # PSF LICENSE AGREEMENT FOR PYTHON 2.3
5 # ------------------------------------
6 #
7 # 1. This LICENSE AGREEMENT is between the Python Software Foundation
8 # ("PSF"), and the Individual or Organization ("Licensee") accessing and
9 # otherwise using Python 2.3 software in source or binary form and its
10 # associated documentation.
11 #
12 # 2. Subject to the terms and conditions of this License Agreement, PSF
13 # hereby grants Licensee a nonexclusive, royalty-free, world-wide
14 # license to reproduce, analyze, test, perform and/or display publicly,
15 # prepare derivative works, distribute, and otherwise use Python 2.3
16 # alone or in any derivative version, provided, however, that PSF's
17 # License Agreement and PSF's notice of copyright, i.e., "Copyright (c)
18 # 2001, 2002, 2003, 2004 Python Software Foundation; All Rights Reserved" are
19 # retained in Python 2.3 alone or in any derivative version prepared by
20 # Licensee.
21 #
22 # 3. In the event Licensee prepares a derivative work that is based on
23 # or incorporates Python 2.3 or any part thereof, and wants to make
24 # the derivative work available to others as provided herein, then
25 # Licensee hereby agrees to include in any such work a brief summary of
26 # the changes made to Python 2.3.
27 #
28 # 4. PSF is making Python 2.3 available to Licensee on an "AS IS"
29 # basis. PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
30 # IMPLIED. BY WAY OF EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND
31 # DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
32 # FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON 2.3 WILL NOT
33 # INFRINGE ANY THIRD PARTY RIGHTS.
34 #
35 # 5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
36 # 2.3 FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS
37 # A RESULT OF MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 2.3,
38 # OR ANY DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
39 #
40 # 6. This License Agreement will automatically terminate upon a material
41 # breach of its terms and conditions.
42 #
43 # 7. Nothing in this License Agreement shall be deemed to create any
44 # relationship of agency, partnership, or joint venture between PSF and
45 # Licensee. This License Agreement does not grant permission to use PSF
46 # trademarks or trade name in a trademark sense to endorse or promote
47 # products or services of Licensee, or any third party.
48 #
49 # 8. By copying, installing or otherwise using Python 2.3, Licensee
50 # agrees to be bound by the terms and conditions of this License
51 # Agreement.
52 #
53 # Modifications: Copyright (c) 2005 Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
54 # - add support for excluding a list of file descriptors from being
55 # closed, allowing access to those file descriptors from the command.
56 #
58 """Spawn a command with pipes to its stdin, stdout, and optionally stderr.
60 The normal os.popen(cmd, mode) call spawns a shell command and provides a
61 file interface to just the input or output of the process depending on
62 whether mode is 'r' or 'w'. This module provides the functions xpopen2(cmd)
63 and xpopen3(cmd) which return two or three pipes to the spawned command.
64 Optionally exclude a list of file descriptors from being closed, allowing
65 access to those file descriptors from the command.
66 """
68 import os
69 import sys
71 try:
72 MAXFD = os.sysconf('SC_OPEN_MAX')
73 except (AttributeError, ValueError):
74 MAXFD = 256
76 _active = []
78 def _cleanup():
79 for inst in _active[:]:
80 inst.poll()
82 class xPopen3:
83 """Class representing a child process. Normally instances are created
84 by the factory functions popen2() and popen3()."""
86 sts = -1 # Child not completed yet
88 def __init__(self, cmd, capturestderr=False, bufsize=-1, passfd=()):
89 """The parameter 'cmd' is the shell command to execute in a
90 sub-process. The 'capturestderr' flag, if true, specifies that
91 the object should capture standard error output of the child process.
92 The default is false. If the 'bufsize' parameter is specified, it
93 specifies the size of the I/O buffers to/from the child process."""
94 _cleanup()
95 self.passfd = passfd
96 p2cread, p2cwrite = os.pipe()
97 c2pread, c2pwrite = os.pipe()
98 if capturestderr:
99 errout, errin = os.pipe()
100 self.pid = os.fork()
101 if self.pid == 0:
102 # Child
103 os.dup2(p2cread, 0)
104 os.dup2(c2pwrite, 1)
105 if capturestderr:
106 os.dup2(errin, 2)
107 self._run_child(cmd)
108 os.close(p2cread)
109 self.tochild = os.fdopen(p2cwrite, 'w', bufsize)
110 os.close(c2pwrite)
111 self.fromchild = os.fdopen(c2pread, 'r', bufsize)
112 if capturestderr:
113 os.close(errin)
114 self.childerr = os.fdopen(errout, 'r', bufsize)
115 else:
116 self.childerr = None
117 _active.append(self)
119 def _run_child(self, cmd):
120 if isinstance(cmd, basestring):
121 cmd = ['/bin/sh', '-c', cmd]
122 for i in range(3, MAXFD):
123 if i in self.passfd:
124 continue
125 try:
126 os.close(i)
127 except OSError:
128 pass
129 try:
130 os.execvp(cmd[0], cmd)
131 finally:
132 os._exit(127)
134 def poll(self):
135 """Return the exit status of the child process if it has finished,
136 or -1 if it hasn't finished yet."""
137 if self.sts < 0:
138 try:
139 pid, sts = os.waitpid(self.pid, os.WNOHANG)
140 if pid == self.pid:
141 self.sts = sts
142 _active.remove(self)
143 except os.error:
144 pass
145 return self.sts
147 def wait(self):
148 """Wait for and return the exit status of the child process."""
149 if self.sts < 0:
150 pid, sts = os.waitpid(self.pid, 0)
151 if pid == self.pid:
152 self.sts = sts
153 _active.remove(self)
154 return self.sts
157 def xpopen2(cmd, bufsize=-1, mode='t', passfd=[]):
158 """Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
159 specified, it sets the buffer size for the I/O pipes. The file objects
160 (child_stdout, child_stdin) are returned."""
161 inst = xPopen3(cmd, False, bufsize, passfd)
162 return inst.fromchild, inst.tochild
164 def xpopen3(cmd, bufsize=-1, mode='t', passfd=[]):
165 """Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
166 specified, it sets the buffer size for the I/O pipes. The file objects
167 (child_stdout, child_stdin, child_stderr) are returned."""
168 inst = xPopen3(cmd, True, bufsize, passfd)
169 return inst.fromchild, inst.tochild, inst.childerr