1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
"""Spawn a command with pipes to its stdin, stdout, and optionally stderr.
The normal os.popen(cmd, mode) call spawns a shell command and provides a
file interface to just the input or output of the process depending on
whether mode is 'r' or 'w'. This module provides the functions popen2(cmd)
and popen3(cmd) which return two or three pipes to the spawned command.
"""
import os
import sys
import types
__all__ = ["popen2", "popen3", "popen4"]
MAXFD = 256 # Max number of file descriptors (os.getdtablesize()???)
_active = []
def _cleanup():
for inst in _active[:]:
inst.poll()
class Popen3:
"""Class representing a child process. Normally instances are created
by the factory functions popen2() and popen3()."""
sts = -1 # Child not completed yet
def __init__(self, cmd, capturestderr=0, bufsize=-1):
"""The parameter 'cmd' is the shell command to execute in a
sub-process. The 'capturestderr' flag, if true, specifies that
the object should capture standard error output of the child process.
The default is false. If the 'bufsize' parameter is specified, it
specifies the size of the I/O buffers to/from the child process."""
_cleanup()
p2cread, p2cwrite = os.pipe()
c2pread, c2pwrite = os.pipe()
if capturestderr:
errout, errin = os.pipe()
self.pid = os.fork()
if self.pid == 0:
# Child
os.dup2(p2cread, 0)
os.dup2(c2pwrite, 1)
if capturestderr:
os.dup2(errin, 2)
self._run_child(cmd)
os.close(p2cread)
self.tochild = os.fdopen(p2cwrite, 'w', bufsize)
os.close(c2pwrite)
self.fromchild = os.fdopen(c2pread, 'r', bufsize)
if capturestderr:
os.close(errin)
self.childerr = os.fdopen(errout, 'r', bufsize)
else:
self.childerr = None
_active.append(self)
def _run_child(self, cmd):
if isinstance(cmd, types.StringTypes):
cmd = ['/bin/sh', '-c', cmd]
for i in range(3, MAXFD):
try:
os.close(i)
except:
pass
try:
os.execvp(cmd[0], cmd)
finally:
os._exit(1)
def poll(self):
"""Return the exit status of the child process if it has finished,
or -1 if it hasn't finished yet."""
if self.sts < 0:
try:
pid, sts = os.waitpid(self.pid, os.WNOHANG)
if pid == self.pid:
self.sts = sts
_active.remove(self)
except os.error:
pass
return self.sts
def wait(self):
"""Wait for and return the exit status of the child process."""
pid, sts = os.waitpid(self.pid, 0)
if pid == self.pid:
self.sts = sts
_active.remove(self)
return self.sts
class Popen4(Popen3):
childerr = None
def __init__(self, cmd, bufsize=-1):
_cleanup()
p2cread, p2cwrite = os.pipe()
c2pread, c2pwrite = os.pipe()
self.pid = os.fork()
if self.pid == 0:
# Child
os.dup2(p2cread, 0)
os.dup2(c2pwrite, 1)
os.dup2(c2pwrite, 2)
self._run_child(cmd)
os.close(p2cread)
self.tochild = os.fdopen(p2cwrite, 'w', bufsize)
os.close(c2pwrite)
self.fromchild = os.fdopen(c2pread, 'r', bufsize)
_active.append(self)
if sys.platform[:3] == "win":
# Some things don't make sense on non-Unix platforms.
del Popen3, Popen4
def popen2(cmd, bufsize=-1, mode='t'):
"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
specified, it sets the buffer size for the I/O pipes. The file objects
(child_stdout, child_stdin) are returned."""
w, r = os.popen2(cmd, mode, bufsize)
return r, w
def popen3(cmd, bufsize=-1, mode='t'):
"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
specified, it sets the buffer size for the I/O pipes. The file objects
(child_stdout, child_stdin, child_stderr) are returned."""
w, r, e = os.popen3(cmd, mode, bufsize)
return r, w, e
def popen4(cmd, bufsize=-1, mode='t'):
"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
specified, it sets the buffer size for the I/O pipes. The file objects
(child_stdout_stderr, child_stdin) are returned."""
w, r = os.popen4(cmd, mode, bufsize)
return r, w
else:
def popen2(cmd, bufsize=-1, mode='t'):
"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
specified, it sets the buffer size for the I/O pipes. The file objects
(child_stdout, child_stdin) are returned."""
inst = Popen3(cmd, 0, bufsize)
return inst.fromchild, inst.tochild
def popen3(cmd, bufsize=-1, mode='t'):
"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
specified, it sets the buffer size for the I/O pipes. The file objects
(child_stdout, child_stdin, child_stderr) are returned."""
inst = Popen3(cmd, 1, bufsize)
return inst.fromchild, inst.tochild, inst.childerr
def popen4(cmd, bufsize=-1, mode='t'):
"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
specified, it sets the buffer size for the I/O pipes. The file objects
(child_stdout_stderr, child_stdin) are returned."""
inst = Popen4(cmd, bufsize)
return inst.fromchild, inst.tochild
__all__.extend(["Popen3", "Popen4"])
def _test():
cmd = "cat"
teststr = "ab cd\n"
if os.name == "nt":
cmd = "more"
# "more" doesn't act the same way across Windows flavors,
# sometimes adding an extra newline at the start or the
# end. So we strip whitespace off both ends for comparison.
expected = teststr.strip()
print "testing popen2..."
r, w = popen2(cmd)
w.write(teststr)
w.close()
got = r.read()
if got.strip() != expected:
raise ValueError("wrote %s read %s" % (`teststr`, `got`))
print "testing popen3..."
try:
r, w, e = popen3([cmd])
except:
r, w, e = popen3(cmd)
w.write(teststr)
w.close()
got = r.read()
if got.strip() != expected:
raise ValueError("wrote %s read %s" % (`teststr`, `got`))
got = e.read()
if got:
raise ValueError("unexected %s on stderr" % `got`)
for inst in _active[:]:
inst.wait()
if _active:
raise ValueError("_active not empty")
print "All OK"
if __name__ == '__main__':
_test()
|
