'\" te
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.TH posix_openpt 3C "1 Dec 2003" "SunOS 5.11" "Standard C Library Functions"
.SH NAME
posix_openpt \- open a pseudo terminal device
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>
#include <fcntl.h>

\fBint\fR \fBposix_openpt\fR(\fBint\fR \fIoflag\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBposix_openpt()\fR function establishes a connection between a master
device for a pseudo-terminal and a file descriptor. The file descriptor is used
by other I/O functions that refer to that pseudo-terminal.
.sp
.LP
The file status flags and file access modes of the open file description are
set according to the value of \fIoflag\fR.
.sp
.LP
Values for \fIoflag\fR are constructed by a bitwise-inclusive OR of flags from
the following list, defined in <\fBfcntl.h\fR>.
.sp
.ne 2
.mk
.na
\fB\fBO_RDWR\fR\fR
.ad
.RS 12n
.rt  
Open for reading and writing.
.RE

.sp
.ne 2
.mk
.na
\fB\fBO_NOCTTY\fR\fR
.ad
.RS 12n
.rt  
If set, \fBposix_openpt()\fR does not cause the terminal device to become the
controlling terminal for the process.
.RE

.sp
.LP
The behavior of other values for the \fIoflag\fR argument is unspecified.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, the \fBposix_openpt()\fR function opens a master
pseudo-terminal device and returns a non-negative integer representing the
lowest numbered unused file descriptor. Otherwise, -1 is returned and
\fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBposix_openpt()\fR function will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEMFILE\fR\fR
.ad
.RS 10n
.rt  
{\fBOPEN_MAX\fR} file descriptors are currently open in the calling process.
.RE

.sp
.ne 2
.mk
.na
\fB\fBENFILE\fR\fR
.ad
.RS 10n
.rt  
The maximum allowable number of files is currently open in the system.
.RE

.sp
.LP
The \fBposix_openpt()\fR function may fail if:
.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
The value of \fIoflag\fR is not valid.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
.rt  
Out of pseudo-terminal resources.
.RE

.sp
.ne 2
.mk
.na
\fB\fBENOSR\fR\fR
.ad
.RS 10n
.rt  
Out of STREAMS resources.
.RE

.SH EXAMPLES
.LP
\fBExample 1 \fROpen a pseudo-terminal.
.sp
.LP
The following example opens a pseudo-terminal and returns the name of the slave
device and a file descriptor.

.sp
.in +2
.nf
#include fcntl.h>
#include stdio.h>

int masterfd, slavefd;
char *slavedevice;

masterfd = posix_openpt(O_RDWR|O_NOCTTY);

if (masterfd == -1
      || grantpt (masterfd) == -1
      || unlockpt (masterfd) == -1
      || (slavedevice = ptsname (masterfd)) == NULL)
      return -1;

printf("slave device is: %s\en", slavedevice);

slavefd = open(slave, O_RDWR|O_NOCTTY);
if (slavefd < 0)
      return -1;
.fi
.in -2

.SH USAGE
.sp
.LP
This function provides a method for portably obtaining a file descriptor of a
master terminal device for a pseudo-terminal. The \fBgrantpt\fR(3C) and
\fBptsname\fR(3C) functions can be used to manipulate mode and ownership
permissions and to obtain the name of the slave device, respectively.
.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 StabilityStandard
_
MT-LevelMT-Safe
.TE

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