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.\"     @(#)ctermid.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: head/lib/libc/gen/ctermid.3 225897 2011-10-01 12:19:48Z ed $
.\"
.Dd October 1, 2011
.Dt CTERMID 3
.Os
.Sh NAME
.Nm ctermid
.Nd generate terminal pathname
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft char *
.Fn ctermid "char *buf"
.Ft char *
.Fn ctermid_r "char *buf"
.Sh DESCRIPTION
The
.Fn ctermid
function generates a string, that, when used as a pathname, refers to
the current controlling terminal of the calling process.
.Pp
If
.Fa buf
is the
.Dv NULL
pointer, a pointer to a static area is returned.
Otherwise, the pathname is copied into the memory referenced by
.Fa buf .
The argument
.Fa buf
is assumed to be at least
.Dv L_ctermid
(as defined in the include
file
.In stdio.h )
bytes long.
.Pp
The
.Fn ctermid_r
function
provides the same functionality as
.Fn ctermid
except that if
.Fa buf
is a
.Dv NULL
pointer,
.Dv NULL
is returned.
.Pp
If no suitable lookup of the controlling terminal name can be performed,
this implementation returns
.Ql /dev/tty .
.Sh RETURN VALUES
Upon successful completion, a
.Pf non- Dv NULL
pointer is returned.
Otherwise, a
.Dv NULL
pointer is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
The current implementation detects no error conditions.
.Sh SEE ALSO
.Xr ttyname 3
.Sh STANDARDS
The
.Fn ctermid
function conforms to
.St -p1003.1-88 .
.Sh BUGS
By default the
.Fn ctermid
function
writes all information to an internal static object.
Subsequent calls to
.Fn ctermid
will modify the same object.