man3/ptsname.3

.\" %%%LICENSE_START(PUBLIC_DOMAIN)
.\" This page is in the public domain. - aeb
.\" %%%LICENSE_END
.\"
.\" 2004-12-17, mtk, added description of ptsname_r() + ERRORS
.\"
.TH PTSNAME 3 2020-06-09 "" "Linux Programmer's Manual"
.SH NAME
ptsname, ptsname_r \- get the name of the terminal corresponding to a pseudoterminal
.SH SYNOPSIS
.B #include <stdlib.h>
.PP
.BI "char *ptsname(int " fd ");"
.br
.BI "int ptsname_r(int " fd ", char *" buf ", size_t " buflen ");"
.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PP
.ad l
.BR ptsname ():
.br
.RS 4
Since glibc 2.24:
    _XOPEN_SOURCE\ >=\ 500 ||
        (_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED)
.br
Glibc 2.23 and earlier:
    _XOPEN_SOURCE
.RE
.PP
.BR ptsname_r ():
    _GNU_SOURCE
.ad
.SH DESCRIPTION
The
.BR ptsname ()
function returns the name of the terminal device
corresponding to the pseudoterminal device referred to by the file descriptor
.IR fd .
.PP
The
.BR ptsname_r ()
function is the reentrant equivalent of
.BR ptsname ().
It returns the name of the terminal device as a
null-terminated string in the buffer pointed to by
.IR buf .
The
.I buflen
argument specifies the number of bytes available in
.IR buf .
.SH RETURN VALUE
On success,
.BR ptsname ()
returns a pointer to a string in static storage which will be
overwritten by subsequent calls.
This pointer must not be freed.
On failure, NULL is returned.
.PP
On success,
.BR ptsname_r ()
returns 0.
On failure, an error number is returned to indicate the error.
.\" In glibc, the error number is not only returned as the return value
.\" but also stored in errno. But this is not true for musl libc.
.SH ERRORS
.TP
.B EINVAL
.RB ( ptsname_r ()
only)
.I buf
is NULL.
(This error is returned only for
.\" glibc commit 8f0a947cf55f3b0c4ebdf06953c57eff67a22fa9
glibc 2.25 and earlier.)
.TP
.B ENOTTY
.I fd
does not refer to a pseudoterminal device.
.TP
.B ERANGE
.RB ( ptsname_r ()
only)
.I buf
is too small.
.SH VERSIONS
.BR ptsname ()
is provided in glibc since version 2.1.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface	Attribute	Value
T{
.BR ptsname ()
T}	Thread safety	MT-Unsafe race:ptsname
T{
.BR ptsname_r ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
.BR ptsname ():
 POSIX.1-2001, POSIX.1-2008.
.PP
.BR ptsname ()
is part of the UNIX 98 pseudoterminal support (see
.BR pts (4)).
.PP
.BR ptsname_r ()
is a Linux extension, that is proposed for inclusion
.\" FIXME . for later review when Issue 8 is one day released
.\" http://austingroupbugs.net/tag_view_page.php?tag_id=8
.\" http://austingroupbugs.net/view.php?id=508
in the next major revision of POSIX.1 (Issue 8).
A version of this function is documented on Tru64 and HP-UX, but
on those implementations, \-1 is returned on error, with
.I errno
set to indicate the error.
Avoid using this function in portable programs.
.SH SEE ALSO
.BR grantpt (3),
.BR posix_openpt (3),
.BR ttyname (3),
.BR unlockpt (3),
.BR pts (4),
.BR pty (7)