187 lines
5.5 KiB
C
187 lines
5.5 KiB
C
/* detach.c
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Detach from the controlling terminal.
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Copyright (C) 1992 Ian Lance Taylor
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This file is part of the Taylor UUCP package.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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The author of the program may be contacted at ian@airs.com or
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c/o Infinity Development Systems, P.O. Box 520, Waltham, MA 02254.
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*/
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#include "uucp.h"
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#include "uudefs.h"
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#include "system.h"
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#include "sysdep.h"
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#include <errno.h>
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#if HAVE_SYS_IOCTL_H
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#include <sys/ioctl.h>
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#endif
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#ifdef TIOCNOTTY
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#define HAVE_TIOCNOTTY 1
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#else
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#define HAVE_TIOCNOTTY 0
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#endif
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#if HAVE_FCNTL_H
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#include <fcntl.h>
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#else
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#if HAVE_SYS_FILE_H
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#include <sys/file.h>
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#endif
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#endif
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#ifndef O_RDONLY
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#define O_RDONLY 0
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#define O_WRONLY 1
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#define O_RDWR 2
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#endif
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/* Detach from the controlling terminal. This is called by uucico if
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it is calling out to another system, so that it can receive SIGHUP
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signals from the port it calls out on. It is also called by uucico
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just before it starts uuxqt, so that uuxqt is completely
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independent of the terminal. */
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void
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usysdep_detach ()
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{
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#if ! HAVE_BSD_PGRP || ! HAVE_TIOCNOTTY
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pid_t igrp;
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/* First make sure we are not a process group leader. If we have
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TIOCNOTTY, this doesn't matter, since TIOCNOTTY sets our process
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group to 0 anyhow. */
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#if HAVE_BSD_PGRP
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igrp = getpgrp (0);
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#else
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igrp = getpgrp ();
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#endif
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if (igrp == getpid ())
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{
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boolean fignored;
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pid_t ipid;
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/* Ignore SIGHUP, since our process group leader is about to
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die. */
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usset_signal (SIGHUP, SIG_IGN, FALSE, &fignored);
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ipid = ixsfork ();
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if (ipid < 0)
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ulog (LOG_FATAL, "fork: %s", strerror (errno));
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if (ipid != 0)
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_exit (EXIT_SUCCESS);
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/* We'll always wind up as a child of process number 1, right?
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Right? We have to wait for our parent to die before
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reenabling SIGHUP. */
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while (getppid () != 1)
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sleep (1);
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ulog_id (getpid ());
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/* Restore SIGHUP catcher if it wasn't being ignored. */
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if (! fignored)
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usset_signal (SIGHUP, ussignal, TRUE, (boolean *) NULL);
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}
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#endif /* ! HAVE_BSD_PGRP || ! HAVE_TIOCNOTTY */
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#if HAVE_TIOCNOTTY
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/* Lose the original controlling terminal. If standard input has
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been reopened to /dev/null, this will do no harm. If another
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port has been opened to become the controlling terminal, it
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should have been detached when it was closed. */
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(void) ioctl (0, TIOCNOTTY, (char *) NULL);
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#endif
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/* Close stdin, stdout and stderr and reopen them on /dev/null, to
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make sure we have no connection at all to the terminal. */
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(void) close (0);
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(void) close (1);
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(void) close (2);
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if (open ((char *) "/dev/null", O_RDONLY) != 0
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|| open ((char *) "/dev/null", O_WRONLY) != 1
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|| open ((char *) "/dev/null", O_WRONLY) != 2)
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ulog (LOG_FATAL, "open (/dev/null): %s", strerror (errno));
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#if HAVE_BSD_PGRP
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/* Make sure our process group ID is set to 0. On BSD TIOCNOTTY
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should already have set it 0, so this will do no harm. On System
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V we presumably did not execute the TIOCNOTTY call, but the
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System V setpgrp will detach the controlling terminal anyhow.
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This lets us use the same code on both BSD and System V, provided
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it compiles correctly, which life easier for the configure
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script. We don't output an error if we got EPERM because some
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BSD variants don't permit this usage of setpgrp (which means they
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don't provide any way to pick up a new controlling terminal). */
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if (setpgrp (0, 0) < 0)
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{
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if (errno != EPERM)
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ulog (LOG_ERROR, "setpgrp: %s", strerror (errno));
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}
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#else /* ! HAVE_BSD_PGRP */
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#if HAVE_SETSID
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/* Under POSIX the setsid call creates a new session for which we
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are the process group leader. It also detaches us from our
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controlling terminal. I'm using the BSD setpgrp call first
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because they should be equivalent for my purposes, but it turns
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out that on Ultrix 4.0 setsid prevents us from ever acquiring
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another controlling terminal (it does not change our process
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group, and Ultrix 4.0 prevents us from setting our process group
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to 0). */
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(void) setsid ();
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#else /* ! HAVE_SETSID */
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#if HAVE_SETPGRP
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/* Now we assume we have the System V setpgrp, which takes no
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arguments, and we couldn't compile the HAVE_BSD_PGRP code above
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because there was a prototype somewhere in scope. On System V
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setpgrp makes us the leader of a new process group and also
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detaches the controlling terminal. */
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if (setpgrp () < 0)
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ulog (LOG_ERROR, "setpgrp: %s", strerror (errno));
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#else /* ! HAVE_SETPGRP */
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#error Must detach from controlling terminal
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#endif /* HAVE_SETPGRP */
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#endif /* ! HAVE_SETSID */
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#endif /* ! HAVE_BSD_PGRP */
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/* At this point we have completely detached from our controlling
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terminal. The next terminal device we open will probably become
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our controlling terminal. */
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}
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