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Annotation of coherent/g/usr/lib/uucp/tay104/unix/detach.c, revision 1.1

1.1     ! root        1: /* detach.c
        !             2:    Detach from the controlling terminal.
        !             3: 
        !             4:    Copyright (C) 1992 Ian Lance Taylor
        !             5: 
        !             6:    This file is part of the Taylor UUCP package.
        !             7: 
        !             8:    This program is free software; you can redistribute it and/or
        !             9:    modify it under the terms of the GNU General Public License as
        !            10:    published by the Free Software Foundation; either version 2 of the
        !            11:    License, or (at your option) any later version.
        !            12: 
        !            13:    This program is distributed in the hope that it will be useful, but
        !            14:    WITHOUT ANY WARRANTY; without even the implied warranty of
        !            15:    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            16:    General Public License for more details.
        !            17: 
        !            18:    You should have received a copy of the GNU General Public License
        !            19:    along with this program; if not, write to the Free Software
        !            20:    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            21: 
        !            22:    The author of the program may be contacted at [email protected] or
        !            23:    c/o Infinity Development Systems, P.O. Box 520, Waltham, MA 02254.
        !            24:    */
        !            25: 
        !            26: #include "uucp.h"
        !            27: 
        !            28: #include "uudefs.h"
        !            29: #include "system.h"
        !            30: #include "sysdep.h"
        !            31: 
        !            32: #include <errno.h>
        !            33: 
        !            34: #if HAVE_SYS_IOCTL_H
        !            35: #include <sys/ioctl.h>
        !            36: #endif
        !            37: 
        !            38: #ifdef TIOCNOTTY
        !            39: #define HAVE_TIOCNOTTY 1
        !            40: #else
        !            41: #define HAVE_TIOCNOTTY 0 
        !            42: #endif
        !            43: 
        !            44: #if HAVE_FCNTL_H
        !            45: #include <fcntl.h>
        !            46: #else
        !            47: #if HAVE_SYS_FILE_H
        !            48: #include <sys/file.h>
        !            49: #endif
        !            50: #endif
        !            51: 
        !            52: #ifndef O_RDONLY
        !            53: #define O_RDONLY 0
        !            54: #define O_WRONLY 1
        !            55: #define O_RDWR 2
        !            56: #endif
        !            57: 
        !            58: /* Detach from the controlling terminal.  This is called by uucico if
        !            59:    it is calling out to another system, so that it can receive SIGHUP
        !            60:    signals from the port it calls out on.  It is also called by uucico
        !            61:    just before it starts uuxqt, so that uuxqt is completely
        !            62:    independent of the terminal.  */
        !            63: 
        !            64: void
        !            65: usysdep_detach ()
        !            66: {
        !            67: #if ! HAVE_BSD_PGRP || ! HAVE_TIOCNOTTY
        !            68: 
        !            69:   pid_t igrp;
        !            70: 
        !            71:   /* First make sure we are not a process group leader.  If we have
        !            72:      TIOCNOTTY, this doesn't matter, since TIOCNOTTY sets our process
        !            73:      group to 0 anyhow.  */
        !            74: 
        !            75: #if HAVE_BSD_PGRP
        !            76:   igrp = getpgrp (0);
        !            77: #else
        !            78:   igrp = getpgrp ();
        !            79: #endif
        !            80: 
        !            81:   if (igrp == getpid ())
        !            82:     {
        !            83:       boolean fignored;
        !            84:       pid_t ipid;
        !            85: 
        !            86:       /* Ignore SIGHUP, since our process group leader is about to
        !            87:         die.  */
        !            88:       usset_signal (SIGHUP, SIG_IGN, FALSE, &fignored);
        !            89: 
        !            90:       ipid = ixsfork ();
        !            91:       if (ipid < 0)
        !            92:        ulog (LOG_FATAL, "fork: %s", strerror (errno));
        !            93: 
        !            94:       if (ipid != 0)
        !            95:        _exit (EXIT_SUCCESS);
        !            96: 
        !            97:       /* We'll always wind up as a child of process number 1, right?
        !            98:         Right?  We have to wait for our parent to die before
        !            99:         reenabling SIGHUP.  */
        !           100:       while (getppid () != 1)
        !           101:        sleep (1);
        !           102: 
        !           103:       ulog_id (getpid ());
        !           104: 
        !           105:       /* Restore SIGHUP catcher if it wasn't being ignored.  */
        !           106:       if (! fignored)
        !           107:        usset_signal (SIGHUP, ussignal, TRUE, (boolean *) NULL);
        !           108:     }
        !           109: 
        !           110: #endif /* ! HAVE_BSD_PGRP || ! HAVE_TIOCNOTTY */
        !           111: 
        !           112: #if HAVE_TIOCNOTTY
        !           113:   /* Lose the original controlling terminal.  If standard input has
        !           114:      been reopened to /dev/null, this will do no harm.  If another
        !           115:      port has been opened to become the controlling terminal, it
        !           116:      should have been detached when it was closed.  */
        !           117:   (void) ioctl (0, TIOCNOTTY, (char *) NULL);
        !           118: #endif
        !           119: 
        !           120:   /* Close stdin, stdout and stderr and reopen them on /dev/null, to
        !           121:      make sure we have no connection at all to the terminal.  */
        !           122:   (void) close (0);
        !           123:   (void) close (1);
        !           124:   (void) close (2);
        !           125:   if (open ((char *) "/dev/null", O_RDONLY) != 0
        !           126:       || open ((char *) "/dev/null", O_WRONLY) != 1
        !           127:       || open ((char *) "/dev/null", O_WRONLY) != 2)
        !           128:     ulog (LOG_FATAL, "open (/dev/null): %s", strerror (errno));
        !           129: 
        !           130: #if HAVE_BSD_PGRP
        !           131: 
        !           132:   /* Make sure our process group ID is set to 0.  On BSD TIOCNOTTY
        !           133:      should already have set it 0, so this will do no harm.  On System
        !           134:      V we presumably did not execute the TIOCNOTTY call, but the
        !           135:      System V setpgrp will detach the controlling terminal anyhow.
        !           136:      This lets us use the same code on both BSD and System V, provided
        !           137:      it compiles correctly, which life easier for the configure
        !           138:      script.  We don't output an error if we got EPERM because some
        !           139:      BSD variants don't permit this usage of setpgrp (which means they
        !           140:      don't provide any way to pick up a new controlling terminal).  */
        !           141: 
        !           142:   if (setpgrp (0, 0) < 0)
        !           143:     {
        !           144:       if (errno != EPERM)
        !           145:        ulog (LOG_ERROR, "setpgrp: %s", strerror (errno));
        !           146:     }
        !           147: 
        !           148: #else /* ! HAVE_BSD_PGRP */
        !           149: 
        !           150: #if HAVE_SETSID
        !           151: 
        !           152:   /* Under POSIX the setsid call creates a new session for which we
        !           153:      are the process group leader.  It also detaches us from our
        !           154:      controlling terminal.  I'm using the BSD setpgrp call first
        !           155:      because they should be equivalent for my purposes, but it turns
        !           156:      out that on Ultrix 4.0 setsid prevents us from ever acquiring
        !           157:      another controlling terminal (it does not change our process
        !           158:      group, and Ultrix 4.0 prevents us from setting our process group
        !           159:      to 0).  */
        !           160:   (void) setsid ();
        !           161: 
        !           162: #else /* ! HAVE_SETSID */
        !           163: 
        !           164: #if HAVE_SETPGRP
        !           165: 
        !           166:   /* Now we assume we have the System V setpgrp, which takes no
        !           167:      arguments, and we couldn't compile the HAVE_BSD_PGRP code above
        !           168:      because there was a prototype somewhere in scope.  On System V
        !           169:      setpgrp makes us the leader of a new process group and also
        !           170:      detaches the controlling terminal.  */
        !           171: 
        !           172:   if (setpgrp () < 0)
        !           173:     ulog (LOG_ERROR, "setpgrp: %s", strerror (errno));
        !           174: 
        !           175: #else /* ! HAVE_SETPGRP */
        !           176: 
        !           177:  #error Must detach from controlling terminal
        !           178: 
        !           179: #endif /* HAVE_SETPGRP */
        !           180: #endif /* ! HAVE_SETSID */
        !           181: #endif /* ! HAVE_BSD_PGRP */
        !           182: 
        !           183:   /* At this point we have completely detached from our controlling
        !           184:      terminal.  The next terminal device we open will probably become
        !           185:      our controlling terminal.  */
        !           186: }

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