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.\" %%%LICENSE_START(PUBLIC_DOMAIN)
.\" This page is in the public domain. - aeb
.\" %%%LICENSE_END
.\"
.TH UNLOCKPT 3 2017-07-13 "" "Linux Programmer's Manual"
.SH NAME
unlockpt \- unlock a pseudoterminal device pair
.SH SYNOPSIS
.B #define _XOPEN_SOURCE
.br
.B #include <stdlib.h>
.PP
.BI "int unlockpt(int " fd ");"
.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PP
.ad l
.BR unlockpt ():
.br
.RS 4
Since glibc 2.24:
_XOPEN_SOURCE\ >=\ 500 ||
(_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED)
.br
Glibc 2.23 and earlier:
_XOPEN_SOURCE
.RE
.ad
.SH DESCRIPTION
The
.BR unlockpt ()
function unlocks the terminal device
corresponding to the pseudoterminal device referred to by the file descriptor
.IR fd .
.PP
.BR unlockpt ()
should be called before opening the terminal end of
a pseudoterminal device pair.
.SH RETURN VALUE
When successful,
.BR unlockpt ()
returns 0.
Otherwise, it returns \-1 and sets
.I errno
appropriately.
.SH ERRORS
.TP
.B EBADF
The
.I fd
argument is not a file descriptor open for writing.
.TP
.B EINVAL
The
.I fd
argument is not associated with a pseudoterminal device.
.SH VERSIONS
.BR unlockpt ()
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 unlockpt ()
T} Thread safety MT-Safe
.TE
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH SEE ALSO
.BR grantpt (3),
.BR posix_openpt (3),
.BR ptsname (3),
.BR pts (4),
.BR pty (7)