cpython: 8358c68579e9 (original) (raw)

--- a/Lib/subprocess.py +++ b/Lib/subprocess.py @@ -7,343 +7,38 @@

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 +r"""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 older modules and functions: - -os.system -os.spawn* - -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=-1, executable=None,

       stdin=None, stdout=None, stderr=None,[](#l1.27)

       preexec_fn=None, close_fds=True, shell=False,[](#l1.28)

       cwd=None, env=None, universal_newlines=False,[](#l1.29)

       startupinfo=None, creationflags=0,[](#l1.30)

       restore_signals=True, start_new_session=False, pass_fds=(),[](#l1.31)

       *, encoding=None, errors=None):[](#l1.32)

- - -Arguments are: +input/output/error pipes, and obtain their return codes. -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 POSIX, 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 POSIX, 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 will be supplied as the corresponding argument to the io.open() -function when creating the stdin/stdout/stderr pipe file objects: -0 means unbuffered (read & write are one system call and can return short), -1 means line buffered, any other positive value means use a buffer of -approximately that size. A negative bufsize, the default, means the system -default of io.DEFAULT_BUFFER_SIZE will be used. +For a complete description of this module see the Python documentation. -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. - -On POSIX, if preexec_fn is set to a callable object, this object will be -called in the child process just before the child is executed. The use -of preexec_fn is not thread safe, using it in the presence of threads -could lead to a deadlock in the child process before the new executable -is executed. - -If close_fds is true, all file descriptors except 0, 1 and 2 will be -closed before the child process is executed. The default for close_fds -varies by platform: Always true on POSIX. True when stdin/stdout/stderr -are None on Windows, false otherwise. - -pass_fds is an optional sequence of file descriptors to keep open between the -parent and child. Providing any pass_fds implicitly sets close_fds to true. - -if shell is true, the specified command will be executed through the -shell. +Main API +======== +run(...): Runs a command, waits for it to complete, then returns a

     CompletedProcess instance.[](#l1.96)

+Popen(...): A class for flexibly executing a command in a new process -If cwd is not None, the current directory will be changed to cwd -before the child is executed. - -On POSIX, if restore_signals is True all signals that Python sets to -SIG_IGN are restored to SIG_DFL in the child process before the exec. -Currently this includes the SIGPIPE, SIGXFZ and SIGXFSZ signals. This -parameter does nothing on Windows. - -On POSIX, if start_new_session is True, the setsid() system call will be made -in the child process prior to executing the command. - -If env is not None, it defines the environment variables for the new -process. - -If encoding or errors are specified or universal_newlines is True, the file -objects stdout and stderr are opened in text mode. See io.TextIOWrapper for -the interpretation of these parameters are used. - -If no encoding is specified and universal_newlines is False, the file -objects stdin, stdout and stderr are opened as binary files, and no -line ending conversion is done. - -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. -(Windows only) +Constants +--------- +DEVNULL: Special value that indicates that os.devnull should be used +PIPE: Special value that indicates a pipe should be created +STDOUT: Special value that indicates that stderr should go to stdout -This module also defines some shortcut functions: - -call(*popenargs, **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 = subprocess.call(["ls", "-l"])

- -check_call(*popenargs, **kwargs):

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:

subprocess.check_call(["ls", "-l"])
0

- -getstatusoutput(cmd):

Return (status, output) of executing cmd in a shell.

Execute the string 'cmd' in a shell with 'check_output' and
return a 2-tuple (status, output). Universal newlines mode is used,
meaning that the result with be decoded to a string.

A trailing newline is stripped from the output.
The exit status for the command can be interpreted
according to the rules for the function 'wait'. Example:

subprocess.getstatusoutput('ls /bin/ls')
(0, '/bin/ls')
subprocess.getstatusoutput('cat /bin/junk')
(256, 'cat: /bin/junk: No such file or directory')
subprocess.getstatusoutput('/bin/junk')
(256, 'sh: /bin/junk: not found')

- -getoutput(cmd):

Return output (stdout or stderr) of executing cmd in a shell.

Like getstatusoutput(), except the exit status is ignored and the return
value is a string containing the command's output. Example:

subprocess.getoutput('ls /bin/ls')
'/bin/ls'

- -check_output(*popenargs, **kwargs):

Run command with arguments and return its output.

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:

output = subprocess.check_output(["ls", "-l", "/dev/null"])

There is an additional optional argument, "input", allowing you to
pass a string to the subprocess's stdin. If you use this argument
you may not also use the Popen constructor's "stdin" argument.

If universal_newlines is set to True, the "input" argument must
be a string rather than bytes, and the return value will be a string.

- -Exceptions ----------- -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 child's 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. - -Exceptions defined within this module inherit from SubprocessError. -check_call() and check_output() will raise CalledProcessError if the -called process returns a non-zero return code. TimeoutExpired -be raised if a timeout was specified and expired. - - -Security --------- -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. - - -Popen objects -============= -Instances of the Popen class have the following methods: - -poll()

Check if child process has terminated. Returns returncode
attribute.

- -wait()

Wait for child process to terminate. Returns returncode attribute.

- -communicate(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 data to be
sent to the child process, or None, if no data should be sent to
the child. If the Popen instance was constructed in text mode, the
input argument should be a string. Otherwise, it should be bytes.

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: - -stdin

If the stdin argument is PIPE, this attribute is a file object
that provides input to the child process. Otherwise, it is None.

- -stdout

If the stdout argument is PIPE, this attribute is a file object
that provides output from the child process. Otherwise, it is
None.

- -stderr

If the stderr argument is PIPE, this attribute is file object that
provides error output from the child process. Otherwise, it is
None.

- -pid

The process ID of the child process.

- -returncode

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 (POSIX only).

- - -Replacing older functions with the subprocess module -==================================================== -In this section, "a ==> 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("Child was terminated by signal", -retcode, file=sys.stderr)[](#l1.322)

else:

   print("Child returned", retcode, file=sys.stderr)[](#l1.324)

-except OSError as e:

print("Execution failed:", e, file=sys.stderr)

- - -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"}) +Older API +========= +call(...): Runs a command, waits for it to complete, then returns

the return code.

+check_call(...): Same as call() but raises CalledProcessError()

if return code is not 0

+check_output(...): Same as check_call() but returns the contents of

stdout instead of a return code

+getoutput(...): Runs a command in the shell, waits for it to complete,

then returns the output

+getstatusoutput(...): Runs a command in the shell, waits for it to complete,

then returns a (status, output) tuple

""" import sys @@ -363,12 +58,11 @@ class SubprocessError(Exception): pass class CalledProcessError(SubprocessError):

"""Raised when a check_call() or check_output() process returns non-zero.

"""Raised when run() is called with check=True and the process
returns a non-zero exit status.

The exit status will be stored in the returncode attribute, negative
if it represents a signal number.

check_output() will also store the output in the output attribute.

Attributes:
```
 cmd, returncode, stdout, stderr, output[](#l1.385)
```
""" def init(self, returncode, cmd, output=None, stderr=None): self.returncode = returncode

@@ -403,6 +97,9 @@ class CalledProcessError(SubprocessError class TimeoutExpired(SubprocessError): """This exception is raised when the timeout expires while waiting for a child process. +

Attributes:
```
   cmd, output, stdout, stderr, timeout[](#l1.395)
```
""" def init(self, cmd, timeout, output=None, stderr=None): self.cmd = cmd

@@ -841,7 +538,49 @@ def getoutput(cmd): class Popen(object):

""" Execute a child program in a new process.

For a complete description of the arguments see the Python documentation.

Arguments:

 args: A string, or a sequence of program arguments.[](#l1.408)

 bufsize: supplied as the buffering argument to the open() function when[](#l1.410)

     creating the stdin/stdout/stderr pipe file objects[](#l1.411)

 executable: A replacement program to execute.[](#l1.413)

 stdin, stdout and stderr: These specify the executed programs' standard[](#l1.415)

     input, standard output and standard error file handles, respectively.[](#l1.416)

 preexec_fn: (POSIX only) An object to be called in the child process[](#l1.418)

     just before the child is executed.[](#l1.419)

 close_fds: Controls closing or inheriting of file descriptors.[](#l1.421)

 shell: If true, the command will be executed through the shell.[](#l1.423)

 cwd: Sets the current directory before the child is executed.[](#l1.425)

 env: Defines the environment variables for the new process.[](#l1.427)

 universal_newlines: If true, use universal line endings for file[](#l1.429)

     objects stdin, stdout and stderr.[](#l1.430)

 startupinfo and creationflags (Windows only)[](#l1.432)

 restore_signals (POSIX only)[](#l1.434)

 start_new_session (POSIX only)[](#l1.436)

```
 pass_fds (POSIX only)[](#l1.438)
```

 encoding and errors: Text mode encoding and error handling to use for[](#l1.440)

     file objects stdin, stdout and stderr.[](#l1.441)

Attributes:

   stdin, stdout, stderr, pid, returncode[](#l1.444)

""" _child_created = False # Set here since del checks it def init(self, args, bufsize=-1, executable=None, @@ -1104,6 +843,8 @@ class Popen(object): def poll(self):

   """Check if child process has terminated. Set and return returncode[](#l1.453)

   attribute."""[](#l1.454)
   return self._internal_poll()[](#l1.455)

--- a/Misc/ACKS +++ b/Misc/ACKS @@ -1013,6 +1013,7 @@ Julien Miotte Andrii V. Mishkovskyi Dom Mitchell Dustin J. Mitchell +Tim Mitchell Zubin Mithra Florian Mladitsch Doug Moen