usr/src/lib/libast/common/comp/setsid.c

   1 /***********************************************************************
   2 *                                                                      *
   3 *               This software is part of the ast package               *
   4 *          Copyright (c) 1985-2010 AT&T Intellectual Property          *
   5 *                      and is licensed under the                       *
   6 *                  Common Public License, Version 1.0                  *
   7 *                    by AT&T Intellectual Property                     *
   8 *                                                                      *
   9 *                A copy of the License is available at                 *
  10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
  11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
  12 *                                                                      *
  13 *              Information and Software Systems Research               *
  14 *                            AT&T Research                             *
  15 *                           Florham Park NJ                            *
  16 *                                                                      *
  17 *                 Glenn Fowler <gsf@research.att.com>                  *
  18 *                  David Korn <dgk@research.att.com>                   *
  19 *                   Phong Vo <kpv@research.att.com>                    *
  20 *                                                                      *
  21 ***********************************************************************/
  22 #pragma prototyped
  23
  24 #include <ast.h>
  25
  26 #if _lib_setsid
  27
  28 NoN(setsid)
  29
  30 #else
  31
  32 #include <ast_tty.h>
  33 #include <error.h>
  34
  35 /*
  36  * become new process group leader and drop control tty
  37  */
  38
  39 pid_t
  40 setsid(void)
  41 {
  42         int     pg;
  43 #ifdef TIOCNOTTY
  44         int     fd;
  45 #endif
  46
  47         /*
  48          * become a new process group leader
  49          */
  50
  51         if ((pg = getpid()) == getpgrp())
  52         {
  53                 errno = EPERM;
  54                 return(-1);
  55         }
  56         setpgid(pg, pg);
  57 #ifdef TIOCNOTTY
  58
  59         /*
  60          * drop the control tty
  61          */
  62
  63         if ((fd = open("/dev/tty", O_RDONLY)) >= 0)
  64         {
  65                 ioctl(fd, TIOCNOTTY, 0);
  66                 close(fd);
  67         }
  68 #else
  69
  70         /*
  71          * second child in s5 to avoid reacquiring the control tty
  72          */
  73
  74 #if _lib_fork && HUH920711 /* some s5's botch this */
  75         switch (fork())
  76         {
  77         case -1:
  78                 exit(1);
  79         case 0:
  80                 break;
  81         default:
  82                 exit(0);
  83         }
  84 #endif
  85
  86 #endif
  87         return(pg);
  88 }
  89
  90 #endif