proc

Table of Content

• Name
• Status
• Description
• Synopsis
• Exceptions
  • proc.ProcError
• Methods
  • proc.command
  • proc.command_ex
  • proc.shell_script
  • proc.start_process
• Author
• Copyright and License

Name

proc

Status

This library is considered production ready.

Description

Utility to create sub process.

Synopsis

from pykit import proc

# execute a shell script

returncode, out, err = proc.shell_script('ls / | grep bin')
print returncode
print out
# output:
# > 0
# > bin
# > sbin

# Or run a command directly.
# Unlike the above snippet, following statement does not start an sh process.

returncode, out, err = proc.command('ls', 'a*', cwd='/usr/local')

# a.py
import sys

with open('foo', 'w') as f:
    f.write(str(sys.argv))

# b.py
import time
from pykit import proc

proc.start_daemon('python', './a.py', 'test')
time.sleep(1)
try:
    with open('foo', 'r') as f:
        print repr(f.read())
except Exception as e:
    print repr(e)

Exceptions

proc.ProcError

syntax: proc.ProcError(returncode, out, err, cmd, arguments, options)

It is raised if a sub process return code is not 0. Besides ProcError.args, extended from super class Exception, it has 6 other attributes.

attributes:

• ProcError.returncode: process exit code.
• ProcError.out: stdout in one string.
• ProcError.err: stderr in one string.
• ProcError.cmd: the command a process exec().
• ProcError.arguments: tuple of command arguments.
• ProcError.options: other options passed to this process. Such as close_fds, cwd etc.

Methods

proc.command

syntax: proc.command(cmd, *arguments, **options)

Run a command with arguments arguments in a subprocess. It blocks until sub process exit.

arguments:

• cmd: The path of executable to run.

• arguments: is tuple or list of arguments passed to cmd.

• options: is a dictionary or additional options:

  • close_fds: specifies whether to close all open file descriptor when fork(). By default it is True.

  • cwd: specifies working dir of the sub process. By default it is None, which means does not change current working dir.

  • env: is a dictionary to pass environment variables to sub process.

  • stdin: is a string used as stdin for sub process. By default it is None.

return: a 3 element tuple that contains:

• returncode: sub process exit code in int.
• out: sub process stdout in a single string.
• err: sub process stderr in a single string.

proc.command_ex

syntax: proc.command_ex(cmd, *arguments, **options)

It is the same as proc.command except that if sub process exit code is not 0, it raises exception proc.ProcError.

See proc.ProcError.

return: a 3 element tuple of returncode, out and err, or raise exception proc.ProcError.

proc.shell_script

syntax: proc.shell_script(script_str, **options)

It is just a shortcut of:

options['stdin'] = script_str
return command('sh', **options)

proc.start_process

syntax: proc.start_process(cmd, target, env, *args)

Create a child process and replace it with cmd. Besides stdin, stdout and stderr, all file descriptors from parent process will be closed in the child process. The parent process waits for the child process until it is completed.

arguments:

• cmd: The path of executable to run. Such as sh, bash, python.

• target: The path of the script.

• env: It is a dictionary to pass environment variables to the child process.

• *args: Type is tuple or list. The arguments passed to the script. Type of every element must be str.

return: nothing

Author

Zhang Yanpo (张炎泼) drdr.xp@gmail.com

Copyright and License

The MIT License (MIT)

Copyright (c) 2015 Zhang Yanpo (张炎泼) drdr.xp@gmail.com