Mini Shell

#!/usr/bin/python
# -*- coding: utf-8 -*-

import subprocess


class ExternalProgramFailed(Exception):
    def __init__(self, message):
        Exception.__init__(self, message)


def run_command(cmd, env_data=None):
    """
    Runs external process and returns output
    @param cmd: command and arguments as a list
    @return: string
    """
    cmd_line = ' '.join(cmd)
    try:
        output = subprocess.Popen(
            cmd,
            stdin=open('/dev/null'),
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
            close_fds=True,
            env=env_data)
    except OSError, oserr:
        raise ExternalProgramFailed('%s. Can not run command: %s' % (cmd_line, str(oserr)))
    std_out, std_err = output.communicate()
    if output.returncode != 0:
        raise ExternalProgramFailed(std_err or 'output of the command: %s\n%s' % (cmd_line, std_out))
    return std_out


def delete_line_from_file(path, line):
    """
    Delete line from file. Return True when line(s) have been deleted, False otherwise (specified line is not found)
    :param path: path to file
    :type path: string
    :param line: line to delete without EOL ('\n')
    :type line: string
    :rtype bool
    """
    found = False
    f = open(path, 'r+')
    lines = f.readlines()
    f.seek(0)
    for l in lines:
        if l != ('%s\n' % line):
            f.write(l)
        else:
            found = True
    f.truncate()
    f.close()
    return found