#
# executil.py - generic utility functions for executing programs
#
# Erik Troan <ewt@redhat.com>
#
# Copyright 1999-2002 Red Hat, Inc.
#
# This software may be freely redistributed under the terms of the GNU
# library public license.
#
# You should have received a copy of the GNU Library Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
import os
import sys
import types
import select

#
# pthread_sigmask
#
# Python 2.3 and earlier use pthread_sigmask to block all
# signals right before creating a new thread.  Since exec-ed
# processes inherit the signal mask of the thread that's
# executing them, this causes problems if the exec-ed process
# is expecting a sane signal mask.  Some symptoms include
# unreaped children and parents stuck in waitpid(), among others.
#
use_pthread_sigmask = False
if sys.version_info[:3] < (2, 4, 0):
    try:
        import signal
        import pthread_sigmask
        use_pthread_sigmask = True

        i = 1
        unblock_signal_list = []
        while i < signal.NSIG:
            unblock_signal_list.append(i)
            i = i + 1
    except:
        print """WARNING: You might want to install the pthread_sigmask module.
Python versions earlier than 2.4 have problems with signals and
spawned processes."""
        pass


def getfd(filespec, readOnly = 0):
    if type(filespec) == types.IntType:
        return (filespec, False)
    if filespec == None:
        filespec = "/dev/null"

    flags = os.O_RDWR | os.O_CREAT
    if (readOnly):
        flags = os.O_RDONLY
    fd = os.open(filespec, flags, 0644)
    return (fd, True)

def exec_with_redirect(cmd, argv, stdin=0, stdout=1, stderr=2, setpgrp=True):
    cmd = os.path.abspath(cmd)
    if not os.access (cmd, os.X_OK):
        raise RuntimeError(cmd + " can not be run")

    stdout_opened = False
    stderr_opened = False
    (stdin, stdin_opened) = getfd(stdin)
    if stdout == stderr:
        (stdout, stdout_opened) = getfd(stdout)
        stderr = stdout
    else:
        (stdout, stdout_opened) = getfd(stdout)
        (stderr, stderr_opened) = getfd(stderr)

    childpid = os.fork()
    if (not childpid):
        # Become leader of a new process group if requested
        if setpgrp:
            os.setpgrp()

        if stdin != 0:
            os.dup2(stdin, 0)
            os.close(stdin)
        if stdout != 1:
            os.dup2(stdout, 1)
            if stdout != stderr:
                os.close(stdout)
        if stderr != 2:
            os.dup2(stderr, 2)
            os.close(stderr)

        # Set signal mask to something sane if we can
        if use_pthread_sigmask:
            # Unblock all signals before execing
            (ret, oldmask) = pthread_sigmask.pthread_sigmask(
                    pthread_sigmask.SIG_UNBLOCK,
                    unblock_signal_list)

        try:
            os.execv(cmd, argv)
        except OSError, e:
            print "Could not execute command '%s'.  Reason: %s" % (cmd, e)
        sys.exit(1)

    # Close any files we may have opened
    if stdin_opened:
        os.close(stdin)
    if stdout_opened:
        os.close(stdout)
    if stderr != stdout and stderr_opened:
        os.close(stderr)

    return childpid