'\" t
.\" %%%LICENSE_START(PUBLIC_DOMAIN)
.\" This page is in the public domain. - aeb
.\" %%%LICENSE_END
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.TH unlockpt 3 2023-03-30 "Linux man-pages 6.04"
.SH NAME
unlockpt \- unlock a pseudoterminal master/slave pair
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #define _XOPEN_SOURCE
.B #include <stdlib.h>
.PP
.BI "int unlockpt(int " fd );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR unlockpt ():
.nf
    Since glibc 2.24:
        _XOPEN_SOURCE >= 500
.\"        || (_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED)
    glibc 2.23 and earlier:
        _XOPEN_SOURCE
.fi
.SH DESCRIPTION
The
.BR unlockpt ()
function unlocks the slave pseudoterminal device
corresponding to the master pseudoterminal referred to by the file descriptor
.IR fd .
.PP
.BR unlockpt ()
should be called before opening the slave side of a pseudoterminal.
.SH RETURN VALUE
When successful,
.BR unlockpt ()
returns 0.
Otherwise, it returns \-1 and sets
.I errno
to indicate the error.
.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 master pseudoterminal.
.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 unlockpt ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
glibc 2.1.
POSIX.1-2001.
.SH SEE ALSO
.BR grantpt (3),
.BR posix_openpt (3),
.BR ptsname (3),
.BR pts (4),
.BR pty (7)