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[glibc.git] / termios / tcgetsid.c
blobb83858f420bc5da8c438d7a06bc5cad9597f14a9
1 /* Copyright (C) 1997 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Library General Public License as
6 published by the Free Software Foundation; either version 2 of the
7 License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Library General Public License for more details.
14 You should have received a copy of the GNU Library General Public
15 License along with the GNU C Library; see the file COPYING.LIB. If not,
16 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 Boston, MA 02111-1307, USA. */
19 #include <errno.h>
20 #include <termios.h>
21 #include <sys/ioctl.h>
22 #include <sys/types.h>
23 #include <unistd.h>
25 /* Return the session ID of FD. */
26 pid_t
27 tcgetsid (fd)
28 int fd;
30 pid_t pgrp;
31 pid_t sid;
32 #ifdef TIOCGSID
33 static int tiocgsid_works = 1;
35 if (tiocgsid_works)
37 int serrno = errno;
38 int sid;
40 if (__ioctl (fd, TIOCGSID, &sid) < 0)
42 if (errno == EINVAL)
44 tiocgsid_works = 0;
45 __set_errno (serrno);
47 else
48 return (pid_t) -1;
50 else
51 return (pid_t) sid;
53 #endif
55 pgrp = tcgetpgrp (fd);
56 if (pgrp == -1)
57 return (pid_t) -1;
59 sid = getsid (pgrp);
60 if (sid == -1 && errno == ESRCH)
61 __set_errno (ENOTTY);
63 return sid;