man3/tcgetpgrp.3

.\" Copyright (C) 2002 Andries Brouwer <aeb@cwi.nl>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.TH TCGETPGRP 3 2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
tcgetpgrp, tcsetpgrp \- get and set terminal foreground process group
.SH SYNOPSIS
.nf
.B "#include <unistd.h>"
.PP
.BI "pid_t tcgetpgrp(int " fd );
.BI "int tcsetpgrp(int " fd ", pid_t " pgrp );
.fi
.SH DESCRIPTION
The function
.BR tcgetpgrp ()
returns the process group ID of the foreground process group on the
terminal associated to
.IR fd ,
which must be the controlling terminal of the calling process.
.\" The process itself may be a background process.
.PP
The function
.BR tcsetpgrp ()
makes the process group with process group ID
.I pgrp
the foreground process group on the terminal associated to
.IR fd ,
which must be the controlling terminal of the calling process,
and still be associated with its session.
Moreover,
.I pgrp
must be a (nonempty) process group belonging to
the same session as the calling process.
.PP
If
.BR tcsetpgrp ()
is called by a member of a background process group in its session,
and the calling process is not blocking or ignoring
.BR SIGTTOU ,
a
.B SIGTTOU
signal is sent to all members of this background process group.
.SH RETURN VALUE
When
.I fd
refers to the controlling terminal of the calling process,
the function
.BR tcgetpgrp ()
will return the foreground process group ID of that terminal
if there is one, and some value larger than 1 that is not
presently a process group ID otherwise.
When
.I fd
does not refer to the controlling terminal of the calling process,
\-1 is returned, and
.I errno
is set to indicate the error.
.PP
When successful,
.BR tcsetpgrp ()
returns 0.
Otherwise, it returns \-1, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EBADF
.I fd
is not a valid file descriptor.
.TP
.B EINVAL
.I pgrp
has an unsupported value.
.TP
.B ENOTTY
The calling process does not have a controlling terminal, or
it has one but it is not described by
.IR fd ,
or, for
.BR tcsetpgrp (),
this controlling terminal is no longer associated with the session
of the calling process.
.TP
.B EPERM
.I pgrp
has a supported value, but is not the process group ID of a
process in the same session as the calling process.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR tcgetpgrp (),
.BR tcsetpgrp ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
These functions are implemented via the
.B TIOCGPGRP
and
.B TIOCSPGRP
ioctls.
.SS History
The ioctls appeared in 4.2BSD.
The functions are POSIX inventions.
.SH SEE ALSO
.BR setpgid (2),
.BR setsid (2),
.BR credentials (7)