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/* Copyright (C) 1997-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <unistd.h>
/* Return the session ID of FD. */
pid_t
tcgetsid (int fd)
{
pid_t pgrp;
pid_t sid;
#ifdef TIOCGSID
static int tiocgsid_does_not_work;
if (! tiocgsid_does_not_work)
{
int serrno = errno;
int sid;
if (__ioctl (fd, TIOCGSID, &sid) < 0)
{
if (errno == EINVAL)
{
tiocgsid_does_not_work = 1;
__set_errno (serrno);
}
else
return (pid_t) -1;
}
else
return (pid_t) sid;
}
#endif
pgrp = tcgetpgrp (fd);
if (pgrp == -1)
return (pid_t) -1;
sid = getsid (pgrp);
if (sid == -1 && errno == ESRCH)
__set_errno (ENOTTY);
return sid;
}
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