Mass Deface
b" means that b can be used as a replacement
for a.
Note: All functions in this section fail (more or less) silently if
the executed program cannot be found; this module raises an OSError
exception.
In the following examples, we assume that the subprocess module is
imported with "from subprocess import *".
Replacing /bin/sh shell backquote
---------------------------------
output=`mycmd myarg`
==>
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]
Replacing os.system()
---------------------
sts = os.system("mycmd" + " myarg")
==>
p = Popen("mycmd" + " myarg", shell=True)
pid, sts = os.waitpid(p.pid, 0)
Note:
* Calling the program through the shell is usually not required.
* It's easier to look at the returncode attribute than the
exitstatus.
A more real-world example would look like this:
try:
retcode = call("mycmd" + " myarg", shell=True)
if retcode < 0:
print >>sys.stderr, "Child was terminated by signal", -retcode
else:
print >>sys.stderr, "Child returned", retcode
except OSError, e:
print >>sys.stderr, "Execution failed:", e
Replacing os.spawn*
-------------------
P_NOWAIT example:
pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
==>
pid = Popen(["/bin/mycmd", "myarg"]).pid
P_WAIT example:
retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
==>
retcode = call(["/bin/mycmd", "myarg"])
Vector example:
os.spawnvp(os.P_NOWAIT, path, args)
==>
Popen([path] + args[1:])
Environment example:
os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
==>
Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})
Replacing os.popen*
-------------------
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_stdin,
child_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_stdin,
child_stdout,
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)
On Unix, os.popen2, os.popen3 and os.popen4 also accept a sequence as
the command to execute, in which case arguments will be passed
directly to the program without shell intervention. This usage can be
replaced as follows:
(child_stdin, child_stdout) = os.popen2(["/bin/ls", "-l"], mode,
bufsize)
==>
p = Popen(["/bin/ls", "-l"], bufsize=bufsize, stdin=PIPE, stdout=PIPE)
(child_stdin, child_stdout) = (p.stdin, p.stdout)
Return code handling translates as follows:
pipe = os.popen("cmd", 'w')
...
rc = pipe.close()
if rc is not None and rc % 256:
print "There were some errors"
==>
process = Popen("cmd", 'w', shell=True, stdin=PIPE)
...
process.stdin.close()
if process.wait() != 0:
print "There were some errors"
Replacing popen2.*
------------------
(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)
On Unix, popen2 also accepts a sequence as the command to execute, in
which case arguments will be passed directly to the program without
shell intervention. This usage can be replaced as follows:
(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 popen2.Popen4 basically works as subprocess.Popen,
except that:
* 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.
iNt win32t CalledProcessErrorc B s# e Z d Z d d Z d Z RS( s This exception is raised when a process run by check_call() or
check_output() returns a non-zero exit status.
The exit status will be stored in the returncode attribute;
check_output() will also store the output in the output attribute.
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c O s t | | j S( s 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"])
( R t wait( t popenargst kwargs( ( s" /usr/lib64/python2.7/subprocess.pyR s c O sS t | | } | rO | j d } | d k r= | d } n t | | n d S( sS Run command with arguments. Wait for command to complete. If
the exit code was zero then return, otherwise raise
CalledProcessError. The CalledProcessError object will have the
return code in the returncode attribute.
The arguments are the same as for the Popen constructor. Example:
check_call(["ls", "-l"])
R5 i N( R t getR R ( RW RX t retcodeR ( ( s" /usr/lib64/python2.7/subprocess.pyR s
c O s d | k r t d n t d t | | } | j \ } } | j } | r | j d } | d k r| | d } n t | | d | n | S( s Run command with arguments and return its output as a byte string.
If the exit code was non-zero it raises a CalledProcessError. The
CalledProcessError object will have the return code in the returncode
attribute and output in the output attribute.
The arguments are the same as for the Popen constructor. Example:
>>> check_output(["ls", "-l", "/dev/null"])
'crw-rw-rw- 1 root root 1, 3 Oct 18 2007 /dev/null\n'
The stdout argument is not allowed as it is used internally.
To capture standard error in the result, use stderr=STDOUT.
>>> check_output(["/bin/sh", "-c",
... "ls -l non_existent_file ; exit 0"],
... stderr=STDOUT)
'ls: non_existent_file: No such file or directory\n'
t stdouts3 stdout argument not allowed, it will be overridden.R5 i R N( R, R R t communicateR RY R R ( RW RX t processR t
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c C sG g } t } x+| D]#} g } | r5 | j d n d | k pQ d | k pQ | } | rj | j d n x | D] } | d k r | j | qq | d k r | j d t | d g } | j d qq | r | j | g } n | j | qq W| r| j | n | r | j | | j d q q Wd j | S( s
Translate a sequence of arguments into a command line
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1) Arguments are delimited by white space, which is either a
space or a tab.
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c C s | j | j | j g j d d k rd } d } | j r | r y | j j | Wq t k
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nV | j r t | j j } | j j
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n | j
| | f S| j | S( sf 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).i N( Rv R[ Rw t countR t writeR R2 t EPIPEt EINVALR R7 t readRV t _communicate( R t inputR[ Rw R6 ( ( s" /usr/lib64/python2.7/subprocess.pyR\ s( ' $
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f | f S( s| Construct and return tuple with IO objects:
p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
i N( NNNNNN( NN( NN( NN( t setR t _subprocesst GetStdHandleR t
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c C s+ t j t j | t j d d t j S( s2 Return a duplicate of handle, which is inheritablei i ( R t DuplicateHandlet GetCurrentProcesst DUPLICATE_SAME_ACCESS( R t handle( ( s" /usr/lib64/python2.7/subprocess.pyR q s c C s t j j t j j t j d d } t j j | s t j j t j j t j d } t j j | s t d q n | S( s, Find and return absolut path to w9xpopen.exei s w9xpopen.exesZ Cannot locate w9xpopen.exe, which is needed for Popen to work with your shell or platform.(
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r} t | j n XWd | d k r| | n | d k r| | n | d k r| | n Xt | _ | | _! | | _" | j# d S( s$ Execute program (MS Windows version)t COMSPECs cmd.exes
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c C sF | j d k r? | | j d | k r? | | j | _ q? n | j S( s Check if child process has terminated. Returns returncode
attribute.
This method is called by __del__, so it can only refer to objects
in its local scope.
i N( R R R ( R R& t _WaitForSingleObjectt _WAIT_OBJECT_0t _GetExitCodeProcess( ( s" /usr/lib64/python2.7/subprocess.pyR( s c C sD | j d k r= t j | j t j t j | j | _ n | j S( sO Wait for child process to terminate. Returns returncode
attribute.N( R R R t WaitForSingleObjectR t INFINITEt GetExitCodeProcess( R ( ( s" /usr/lib64/python2.7/subprocess.pyRV s
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c C s | t j k r | j ne | t j k rD t j | j t j n= | t j k rl t j | j t j n t d j | d S( s) Send a signal to the process
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t signalt SIGTERMt terminatet CTRL_C_EVENTR t killRx t CTRL_BREAK_EVENTR, R ( R t sig( ( s" /usr/lib64/python2.7/subprocess.pyt send_signal+ s
c C sv y t j | j d WnX t k
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i i N( R t TerminateProcessR R1 t winerrorR t STILL_ACTIVER ( R R6 t rc( ( s" /usr/lib64/python2.7/subprocess.pyR 7 s c C s t } d \ } } d \ } } d \ } }
| d k r< nX | t k rp | j \ } } | j | | f n$ t | t r | } n | j } | d k r nX | t k r | j \ } } | j | | f n$ t | t r | } n | j } | d k r
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f | f S( s| Construct and return tuple with IO objects:
p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
N( NN( NN( NN( R R R t pipe_cloexect updateRq Rr R R ( R Rv R[ Rw R R R R R R R ( ( s" /usr/lib64/python2.7/subprocess.pyRz L sB c C s~ y
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c C s6 t j \ } } | j | | j | | | f S( s# Create a pipe with FDs set CLOEXEC.( R t pipeR ( R t rt w( ( s" /usr/lib64/python2.7/subprocess.pyR s
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