# subprocess - Subprocesses with accessible I/O streams
# For more information about this module, see PEP 324.
# This module should remain compatible with Python 2.2, see PEP 291.
# Copyright (c) 2003-2005 by Peter Astrand <astrand@lysator.liu.se>
# Licensed to PSF under a Contributor Agreement.
# See http://www.python.org/2.4/license for licensing details.
r
"""subprocess - Subprocesses with accessible I/O streams
This module allows you to spawn processes, connect to their
input/output/error pipes, and obtain their return codes. This module
intends to replace several other, older modules and functions, like:
Information about how the subprocess module can be used to replace these
modules and functions can be found below.
Using the subprocess module
===========================
This module defines one class called Popen:
class Popen(args, bufsize=0, executable=None,
stdin=None, stdout=None, stderr=None,
preexec_fn=None, close_fds=False, shell=False,
cwd=None, env=None, universal_newlines=False,
startupinfo=None, creationflags=0):
args should be a string, or a sequence of program arguments. The
program to execute is normally the first item in the args sequence or
string, but can be explicitly set by using the executable argument.
On UNIX, with shell=False (default): In this case, the Popen class
uses os.execvp() to execute the child program. args should normally
be a sequence. A string will be treated as a sequence with the string
as the only item (the program to execute).
On UNIX, with shell=True: If args is a string, it specifies the
command string to execute through the shell. If args is a sequence,
the first item specifies the command string, and any additional items
will be treated as additional shell arguments.
On Windows: the Popen class uses CreateProcess() to execute the child
program, which operates on strings. If args is a sequence, it will be
converted to a string using the list2cmdline method. Please note that
not all MS Windows applications interpret the command line the same
way: The list2cmdline is designed for applications using the same
rules as the MS C runtime.
bufsize, if given, has the same meaning as the corresponding argument
to the built-in open() function: 0 means unbuffered, 1 means line
buffered, any other positive value means use a buffer of
(approximately) that size. A negative bufsize means to use the system
default, which usually means fully buffered. The default value for
bufsize is 0 (unbuffered).
stdin, stdout and stderr specify the executed programs' standard
input, standard output and standard error file handles, respectively.
Valid values are PIPE, an existing file descriptor (a positive
integer), an existing file object, and None. PIPE indicates that a
new pipe to the child should be created. With None, no redirection
will occur; the child's file handles will be inherited from the
parent. Additionally, stderr can be STDOUT, which indicates that the
stderr data from the applications should be captured into the same
file handle as for stdout.
If preexec_fn is set to a callable object, this object will be called
in the child process just before the child is executed.
If close_fds is true, all file descriptors except 0, 1 and 2 will be
closed before the child process is executed.
if shell is true, the specified command will be executed through the
If cwd is not None, the current directory will be changed to cwd
before the child is executed.
If env is not None, it defines the environment variables for the new
If universal_newlines is true, the file objects stdout and stderr are
opened as a text files, but lines may be terminated by any of '\n',
the Unix end-of-line convention, '\r', the Macintosh convention or
'\r\n', the Windows convention. All of these external representations
are seen as '\n' by the Python program. Note: This feature is only
available if Python is built with universal newline support (the
default). Also, the newlines attribute of the file objects stdout,
stdin and stderr are not updated by the communicate() method.
The startupinfo and creationflags, if given, will be passed to the
underlying CreateProcess() function. They can specify things such as
appearance of the main window and priority for the new process.
This module also defines two shortcut functions:
Run command with arguments. Wait for command to complete, then
return the returncode attribute.
The arguments are the same as for the Popen constructor. Example:
retcode = call(["ls", "-l"])
Exceptions raised in the child process, before the new program has
started to execute, will be re-raised in the parent. Additionally,
the exception object will have one extra attribute called
'child_traceback', which is a string containing traceback information
from the childs point of view.
The most common exception raised is OSError. This occurs, for
example, when trying to execute a non-existent file. Applications
should prepare for OSErrors.
A ValueError will be raised if Popen is called with invalid arguments.
Unlike some other popen functions, this implementation will never call
/bin/sh implicitly. This means that all characters, including shell
metacharacters, can safely be passed to child processes.
Instances of the Popen class have the following methods:
Check if child process has terminated. Returns returncode
Wait for child process to terminate. Returns returncode attribute.
Interact with process: Send data to stdin. Read data from stdout
and stderr, until end-of-file is reached. Wait for process to
terminate. The optional stdin argument should be a string to be
sent to the child process, or None, if no data should be sent to
communicate() returns a tuple (stdout, stderr).
Note: The data read is buffered in memory, so do not use this
method if the data size is large or unlimited.
The following attributes are also available:
If the stdin argument is PIPE, this attribute is a file object
that provides input to the child process. Otherwise, it is None.
If the stdout argument is PIPE, this attribute is a file object
that provides output from the child process. Otherwise, it is
If the stderr argument is PIPE, this attribute is file object that
provides error output from the child process. Otherwise, it is
The process ID of the child process.
The child return code. A None value indicates that the process
hasn't terminated yet. A negative value -N indicates that the
child was terminated by signal N (UNIX only).
Replacing older functions with the subprocess module
====================================================
In this section, "a ==> b" means that b can be used as a replacement
Note: All functions in this section fail (more or less) silently if
the executed program cannot be found; this module raises an OSError
In the following examples, we assume that the subprocess module is
imported with "from subprocess import *".
Replacing /bin/sh shell backquote
---------------------------------
output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0]
Replacing shell pipe line
-------------------------
output=`dmesg | grep hda`
p1 = Popen(["dmesg"], stdout=PIPE)
p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
output = p2.communicate()[0]
sts = os.system("mycmd" + " myarg")
p = Popen("mycmd" + " myarg", shell=True)
sts = os.waitpid(p.pid, 0)
* Calling the program through the shell is usually not required.
* It's easier to look at the returncode attribute than the
A more real-world example would look like this:
retcode = call("mycmd" + " myarg", shell=True)
print >>sys.stderr, "Child was terminated by signal", -retcode
print >>sys.stderr, "Child returned", retcode
print >>sys.stderr, "Execution failed:", e
pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
pid = Popen(["/bin/mycmd", "myarg"]).pid
retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
retcode = call(["/bin/mycmd", "myarg"])
os.spawnvp(os.P_NOWAIT, path, args)
os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})
pipe = os.popen(cmd, mode='r', bufsize)
pipe = Popen(cmd, shell=True, bufsize=bufsize, stdout=PIPE).stdout
pipe = os.popen(cmd, mode='w', bufsize)
pipe = Popen(cmd, shell=True, bufsize=bufsize, stdin=PIPE).stdin
(child_stdin, child_stdout) = os.popen2(cmd, mode, bufsize)
p = Popen(cmd, shell=True, bufsize=bufsize,
stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdin, child_stdout) = (p.stdin, p.stdout)
child_stderr) = os.popen3(cmd, mode, bufsize)
p = Popen(cmd, shell=True, bufsize=bufsize,
stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True)
child_stderr) = (p.stdin, p.stdout, p.stderr)
(child_stdin, child_stdout_and_stderr) = os.popen4(cmd, mode, bufsize)
p = Popen(cmd, shell=True, bufsize=bufsize,
stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True)
(child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout)
Note: If the cmd argument to popen2 functions is a string, the command
is executed through /bin/sh. If it is a list, the command is directly
(child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode)
p = Popen(["somestring"], shell=True, bufsize=bufsize
stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdout, child_stdin) = (p.stdout, p.stdin)
(child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize, mode)
p = Popen(["mycmd", "myarg"], bufsize=bufsize,
stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdout, child_stdin) = (p.stdout, p.stdin)
The popen2.Popen3 and popen3.Popen4 basically works as subprocess.Popen,
* subprocess.Popen raises an exception if the execution fails
* the capturestderr argument is replaced with the stderr argument.
* stdin=PIPE and stdout=PIPE must be specified.
* popen2 closes all filedescriptors by default, but you have to specify
close_fds=True with subprocess.Popen.
mswindows
= (sys
.platform
== "win32")
if 0: # <-- change this to use pywin32 instead of the _subprocess driver
from win32api
import GetStdHandle
, STD_INPUT_HANDLE
, \
STD_OUTPUT_HANDLE
, STD_ERROR_HANDLE
from win32api
import GetCurrentProcess
, DuplicateHandle
, \
GetModuleFileName
, GetVersion
from win32con
import DUPLICATE_SAME_ACCESS
, SW_HIDE
from win32pipe
import CreatePipe
from win32process
import CreateProcess
, STARTUPINFO
, \
GetExitCodeProcess
, STARTF_USESTDHANDLES
, \
STARTF_USESHOWWINDOW
, CREATE_NEW_CONSOLE
from win32event
import WaitForSingleObject
, INFINITE
, WAIT_OBJECT_0
from _subprocess
import *
__all__
= ["Popen", "PIPE", "STDOUT", "call"]
MAXFD
= os
.sysconf("SC_OPEN_MAX")
# True/False does not exist on 2.2.0
def call(*args
, **kwargs
):
"""Run command with arguments. Wait for command to complete, then
return the returncode attribute.
The arguments are the same as for the Popen constructor. Example:
retcode = call(["ls", "-l"])
return Popen(*args
, **kwargs
).wait()
Translate a sequence of arguments into a command line
string, using the same rules as the MS C runtime:
1) Arguments are delimited by white space, which is either a
2) A string surrounded by double quotation marks is
interpreted as a single argument, regardless of white space
contained within. A quoted string can be embedded in an
3) A double quotation mark preceded by a backslash is
interpreted as a literal double quotation mark.
4) Backslashes are interpreted literally, unless they
immediately precede a double quotation mark.
5) If backslashes immediately precede a double quotation mark,
every pair of backslashes is interpreted as a literal
backslash. If the number of backslashes is odd, the last
backslash escapes the next double quotation mark as
# http://msdn.microsoft.com/library/en-us/vccelng/htm/progs_12.asp
# Add a space to separate this argument from the others
needquote
= (" " in arg
) or ("\t" in arg
)
# Don't know if we need to double yet.
result
.append('\\' * len(bs_buf
)*2)
# Add remaining backspaces, if any.
def __init__(self
, args
, bufsize
=0, executable
=None,
stdin
=None, stdout
=None, stderr
=None,
preexec_fn
=None, close_fds
=False, shell
=False,
cwd
=None, env
=None, universal_newlines
=False,
startupinfo
=None, creationflags
=0):
"""Create new Popen instance."""
if not isinstance(bufsize
, (int, long)):
raise TypeError("bufsize must be an integer")
if preexec_fn
is not None:
raise ValueError("preexec_fn is not supported on Windows "
raise ValueError("close_fds is not supported on Windows "
if startupinfo
is not None:
raise ValueError("startupinfo is only supported on Windows "
raise ValueError("creationflags is only supported on Windows "
self
.universal_newlines
= universal_newlines
# Input and output objects. The general principle is like
# p2cwrite ---stdin---> p2cread
# c2pread <--stdout--- c2pwrite
# errread <--stderr--- errwrite
# On POSIX, the child objects are file descriptors. On
# Windows, these are Windows file handles. The parent objects
# are file descriptors on both platforms. The parent objects
# are None when not using PIPEs. The child objects are None
errread
, errwrite
) = self
._get
_handles
(stdin
, stdout
, stderr
)
self
._execute
_child
(args
, executable
, preexec_fn
, close_fds
,
cwd
, env
, universal_newlines
,
startupinfo
, creationflags
, shell
,
self
.stdin
= os
.fdopen(p2cwrite
, 'wb', bufsize
)
self
.stdout
= os
.fdopen(c2pread
, 'rU', bufsize
)
self
.stdout
= os
.fdopen(c2pread
, 'rb', bufsize
)
self
.stderr
= os
.fdopen(errread
, 'rU', bufsize
)
self
.stderr
= os
.fdopen(errread
, 'rb', bufsize
)
def _translate_newlines(self
, data
):
data
= data
.replace("\r\n", "\n")
data
= data
.replace("\r", "\n")
def _get_handles(self
, stdin
, stdout
, stderr
):
"""Construct and return tupel with IO objects:
p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
if stdin
== None and stdout
== None and stderr
== None:
return (None, None, None, None, None, None)
p2cread
, p2cwrite
= None, None
c2pread
, c2pwrite
= None, None
errread
, errwrite
= None, None
p2cread
= GetStdHandle(STD_INPUT_HANDLE
)
p2cread
, p2cwrite
= CreatePipe(None, 0)
# Detach and turn into fd
p2cwrite
= p2cwrite
.Detach()
p2cwrite
= msvcrt
.open_osfhandle(p2cwrite
, 0)
elif type(stdin
) == types
.IntType
:
p2cread
= msvcrt
.get_osfhandle(stdin
)
# Assuming file-like object
p2cread
= msvcrt
.get_osfhandle(stdin
.fileno())
p2cread
= self
._make
_inheritable
(p2cread
)
c2pwrite
= GetStdHandle(STD_OUTPUT_HANDLE
)
c2pread
, c2pwrite
= CreatePipe(None, 0)
# Detach and turn into fd
c2pread
= c2pread
.Detach()
c2pread
= msvcrt
.open_osfhandle(c2pread
, 0)
elif type(stdout
) == types
.IntType
:
c2pwrite
= msvcrt
.get_osfhandle(stdout
)
# Assuming file-like object
c2pwrite
= msvcrt
.get_osfhandle(stdout
.fileno())
c2pwrite
= self
._make
_inheritable
(c2pwrite
)
errwrite
= GetStdHandle(STD_ERROR_HANDLE
)
errread
, errwrite
= CreatePipe(None, 0)
# Detach and turn into fd
errread
= errread
.Detach()
errread
= msvcrt
.open_osfhandle(errread
, 0)
elif type(stderr
) == types
.IntType
:
errwrite
= msvcrt
.get_osfhandle(stderr
)
# Assuming file-like object
errwrite
= msvcrt
.get_osfhandle(stderr
.fileno())
errwrite
= self
._make
_inheritable
(errwrite
)
return (p2cread
, p2cwrite
,
def _make_inheritable(self
, handle
):
"""Return a duplicate of handle, which is inheritable"""
return DuplicateHandle(GetCurrentProcess(), handle
,
GetCurrentProcess(), 0, 1,
def _find_w9xpopen(self
):
"""Find and return absolut path to w9xpopen.exe"""
w9xpopen
= os
.path
.join(os
.path
.dirname(GetModuleFileName(0)),
if not os
.path
.exists(w9xpopen
):
# Eeek - file-not-found - possibly an embedding
# situation - see if we can locate it in sys.exec_prefix
w9xpopen
= os
.path
.join(os
.path
.dirname(sys
.exec_prefix
),
if not os
.path
.exists(w9xpopen
):
raise RuntimeError("Cannot locate w9xpopen.exe, which is "
"needed for Popen to work with your "
def _execute_child(self
, args
, executable
, preexec_fn
, close_fds
,
cwd
, env
, universal_newlines
,
startupinfo
, creationflags
, shell
,
"""Execute program (MS Windows version)"""
if not isinstance(args
, types
.StringTypes
):
args
= list2cmdline(args
)
# Process startup details
default_startupinfo
= STARTUPINFO()
startupinfo
= default_startupinfo
if not None in (p2cread
, c2pwrite
, errwrite
):
startupinfo
.dwFlags |
= STARTF_USESTDHANDLES
startupinfo
.hStdInput
= p2cread
startupinfo
.hStdOutput
= c2pwrite
startupinfo
.hStdError
= errwrite
default_startupinfo
.dwFlags |
= STARTF_USESHOWWINDOW
default_startupinfo
.wShowWindow
= SW_HIDE
comspec
= os
.environ
.get("COMSPEC", "cmd.exe")
args
= comspec
+ " /c " + args
if (GetVersion() >= 0x80000000L
or
os
.path
.basename(comspec
).lower() == "command.com"):
# Win9x, or using command.com on NT. We need to
# use the w9xpopen intermediate program. For more
# information, see KB Q150956
# (http://web.archive.org/web/20011105084002/http://support.microsoft.com/support/kb/articles/Q150/9/56.asp)
w9xpopen
= self
._find
_w
9xpopen
()
args
= '"%s" %s' % (w9xpopen
, args
)
# Not passing CREATE_NEW_CONSOLE has been known to
# cause random failures on win9x. Specifically a
# dialog: "Your program accessed mem currently in
# use at xxx" and a hopeful warning about the
# stability of your system. Cost is Ctrl+C wont
creationflags |
= CREATE_NEW_CONSOLE
hp
, ht
, pid
, tid
= CreateProcess(executable
, args
,
# must inherit handles to pass std
except pywintypes
.error
, e
:
# Translate pywintypes.error to WindowsError, which is
# a subclass of OSError. FIXME: We should really
# translate errno using _sys_errlist (or simliar), but
# how can this be done from Python?
raise WindowsError(*e
.args
)
# Retain the process handle, but close the thread handle
# Child is launched. Close the parent's copy of those pipe
# handles that only the child should have open. You need
# to make sure that no handles to the write end of the
# output pipe are maintained in this process or else the
# pipe will not close when the child process exits and the
"""Check if child process has terminated. Returns returncode
if self
.returncode
== None:
if WaitForSingleObject(self
._handle
, 0) == WAIT_OBJECT_0
:
self
.returncode
= GetExitCodeProcess(self
._handle
)
"""Wait for child process to terminate. Returns returncode
if self
.returncode
== None:
obj
= WaitForSingleObject(self
._handle
, INFINITE
)
self
.returncode
= GetExitCodeProcess(self
._handle
)
def _readerthread(self
, fh
, buffer):
def communicate(self
, input=None):
"""Interact with process: Send data to stdin. Read data from
stdout and stderr, until end-of-file is reached. Wait for
process to terminate. The optional input argument should be a
string to be sent to the child process, or None, if no data
should be sent to the child.
communicate() returns a tuple (stdout, stderr)."""
stdout_thread
= threading
.Thread(target
=self
._readerthread
,
args
=(self
.stdout
, stdout
))
stdout_thread
.setDaemon(True)
stderr_thread
= threading
.Thread(target
=self
._readerthread
,
args
=(self
.stderr
, stderr
))
stderr_thread
.setDaemon(True)
# All data exchanged. Translate lists into strings.
# Translate newlines, if requested. We cannot let the file
# object do the translation: It is based on stdio, which is
# impossible to combine with select (unless forcing no
if self
.universal_newlines
and hasattr(open, 'newlines'):
stdout
= self
._translate
_newlines
(stdout
)
stderr
= self
._translate
_newlines
(stderr
)
def _get_handles(self
, stdin
, stdout
, stderr
):
"""Construct and return tupel with IO objects:
p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
p2cread
, p2cwrite
= None, None
c2pread
, c2pwrite
= None, None
errread
, errwrite
= None, None
p2cread
, p2cwrite
= os
.pipe()
elif type(stdin
) == types
.IntType
:
# Assuming file-like object
c2pread
, c2pwrite
= os
.pipe()
elif type(stdout
) == types
.IntType
:
# Assuming file-like object
c2pwrite
= stdout
.fileno()
errread
, errwrite
= os
.pipe()
elif type(stderr
) == types
.IntType
:
# Assuming file-like object
errwrite
= stderr
.fileno()
return (p2cread
, p2cwrite
,
def _set_cloexec_flag(self
, fd
):
cloexec_flag
= fcntl
.FD_CLOEXEC
old
= fcntl
.fcntl(fd
, fcntl
.F_GETFD
)
fcntl
.fcntl(fd
, fcntl
.F_SETFD
, old | cloexec_flag
)
def _close_fds(self
, but
):
for i
in range(3, MAXFD
):
def _execute_child(self
, args
, executable
, preexec_fn
, close_fds
,
cwd
, env
, universal_newlines
,
startupinfo
, creationflags
, shell
,
"""Execute program (POSIX version)"""
if isinstance(args
, types
.StringTypes
):
args
= ["/bin/sh", "-c"] + args
# For transferring possible exec failure from child to parent
# The first char specifies the exception type: 0 means
# OSError, 1 means some other error.
errpipe_read
, errpipe_write
= os
.pipe()
self
._set
_cloexec
_flag
(errpipe_write
)
# Close parent's pipe ends
# Close pipe fds. Make sure we doesn't close the same
if c2pwrite
and c2pwrite
not in (p2cread
,):
if errwrite
and errwrite
not in (p2cread
, c2pwrite
):
# Close all other fds, if asked for
self
._close
_fds
(but
=errpipe_write
)
os
.execvp(executable
, args
)
os
.execvpe(executable
, args
, env
)
exc_type
, exc_value
, tb
= sys
.exc_info()
# Save the traceback and attach it to the exception object
exc_lines
= traceback
.format_exception(exc_type
,
exc_value
.child_traceback
= ''.join(exc_lines
)
os
.write(errpipe_write
, pickle
.dumps(exc_value
))
# This exitcode won't be reported to applications, so it
# really doesn't matter what we return.
# Wait for exec to fail or succeed; possibly raising exception
data
= os
.read(errpipe_read
, 1048576) # Exceptions limited to 1 MB
child_exception
= pickle
.loads(data
)
def _handle_exitstatus(self
, sts
):
self
.returncode
= -os
.WTERMSIG(sts
)
self
.returncode
= os
.WEXITSTATUS(sts
)
raise RuntimeError("Unknown child exit status!")
"""Check if child process has terminated. Returns returncode
if self
.returncode
== None:
pid
, sts
= os
.waitpid(self
.pid
, os
.WNOHANG
)
self
._handle
_exitstatus
(sts
)
"""Wait for child process to terminate. Returns returncode
if self
.returncode
== None:
pid
, sts
= os
.waitpid(self
.pid
, 0)
self
._handle
_exitstatus
(sts
)
def communicate(self
, input=None):
"""Interact with process: Send data to stdin. Read data from
stdout and stderr, until end-of-file is reached. Wait for
process to terminate. The optional input argument should be a
string to be sent to the child process, or None, if no data
should be sent to the child.
communicate() returns a tuple (stdout, stderr)."""
# Flush stdio buffer. This might block, if the user has
# been writing to .stdin in an uncontrolled fashion.
write_set
.append(self
.stdin
)
read_set
.append(self
.stdout
)
read_set
.append(self
.stderr
)
while read_set
or write_set
:
rlist
, wlist
, xlist
= select
.select(read_set
, write_set
, [])
# When select has indicated that the file is writable,
# we can write up to PIPE_BUF bytes without risk
# blocking. POSIX defines PIPE_BUF >= 512
bytes_written
= os
.write(self
.stdin
.fileno(), input[:512])
input = input[bytes_written
:]
write_set
.remove(self
.stdin
)
data
= os
.read(self
.stdout
.fileno(), 1024)
read_set
.remove(self
.stdout
)
data
= os
.read(self
.stderr
.fileno(), 1024)
read_set
.remove(self
.stderr
)
# All data exchanged. Translate lists into strings.
# Translate newlines, if requested. We cannot let the file
# object do the translation: It is based on stdio, which is
# impossible to combine with select (unless forcing no
if self
.universal_newlines
and hasattr(open, 'newlines'):
stdout
= self
._translate
_newlines
(stdout
)
stderr
= self
._translate
_newlines
(stderr
)
# Example 1: Simple redirection: Get process list
plist
= Popen(["ps"], stdout
=PIPE
).communicate()[0]
# Example 2: Change uid before executing child
p
= Popen(["id"], preexec_fn
=lambda: os
.setuid(100))
# Example 3: Connecting several subprocesses
print "Looking for 'hda'..."
p1
= Popen(["dmesg"], stdout
=PIPE
)
p2
= Popen(["grep", "hda"], stdin
=p1
.stdout
, stdout
=PIPE
)
print repr(p2
.communicate()[0])
# Example 4: Catch execution error
print "Trying a weird file..."
print Popen(["/this/path/does/not/exist"]).communicate()
if e
.errno
== errno
.ENOENT
:
print "The file didn't exist. I thought so..."
print >>sys
.stderr
, "Gosh. No error."
# Example 1: Connecting several subprocesses
print "Looking for 'PROMPT' in set output..."
p1
= Popen("set", stdout
=PIPE
, shell
=True)
p2
= Popen('find "PROMPT"', stdin
=p1
.stdout
, stdout
=PIPE
)
print repr(p2
.communicate()[0])
# Example 2: Simple execution of program
print "Executing calc..."
if __name__
== "__main__":