'\" te
.\" Copyright (c) 1997, The Open Group. All Rights Reserved.
.\" Copyright 1989 AT&T
.\" Portions Copyright (c) 2002, Sun Microsystems, Inc. All Rights Reserved.
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.TH unlockpt 3C "14 Aug 2002" "SunOS 5.11" "Standard C Library Functions"
.SH NAME
unlockpt \- unlock a pseudo-terminal master/slave pair
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBunlockpt\fR(\fBint\fR \fIfildes\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBunlockpt()\fR function unlocks the slave pseudo-terminal device associated with the master to which \fIfildes\fR refers.
.sp
.LP
Portable applications must call \fBunlockpt()\fR before opening the slave side of a pseudo-terminal device.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBunlockpt()\fR returns \fB0\fR. Otherwise, it returns \fB\(mi1\fR and sets \fBerrno\fR to indicate the error.
.SH ERRORS
.sp
.LP
The \fBunlockpt()\fR function may fail if:
.sp
.ne 2
.mk
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
.rt  
The \fIfildes\fR argument is not a file descriptor open for writing.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
The \fIfildes\fR argument is not associated with a master pseudo-terminal device.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelSafe
_
StandardSee \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBopen\fR(2), \fBgrantpt\fR(3C), \fBptsname\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)
.sp
.LP
\fISTREAMS Programming Guide\fR