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.Dd May 4, 2009
.Dt TCSETSID 3
.Os
.Sh NAME
.Nm tcsetsid
.Nd set session ID associated with a controlling terminal
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In termios.h
.Ft int
.Fn tcsetsid "int fd" "pid_t pid"
.Sh DESCRIPTION
The
.Fn tcsetsid
function sets associates a session identified by
.Fa pid
with a controlling terminal specified by
.Fa fd .
.Pp
This implementation only allows the controlling terminal to be changed
by the session leader itself.
This implies that
.Fa pid
always has to be equal to the process ID.
.Pp
It is unsupported to associate with a terminal that already has an
associated session.
Conversely, it is also unsupported to associate to a terminal when
the session is already associated with a different terminal.
.Sh ERRORS
If an error occurs,
.Fn tcsetsid
returns -1 and the global variable
.Va errno
is set to indicate the error, as follows:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid file descriptor.
.It Bq Er ENOTTY
The file descriptor represented by
.Fa fd
is not a terminal.
.It Bq Er EINVAL
The
.Fa pid
argument is not equal to the session ID of the calling process.
.It Bq Er EPERM
The calling process is not a session leader.
.It Bq Er EPERM
The session already has an associated terminal or the terminal already
has an associated session.
.El
.Sh SEE ALSO
.Xr getsid 2 ,
.Xr setsid 2 ,
.Xr tcgetpgrp 3 ,
.Xr tcgetsid 3
.Sh HISTORY
A
.Fn tcsetsid
function first appeared in QNX.
It does not comply to any standard.