POSIX_OPENPT(3C)POSIX_OPENPT(3C)NAMEposix_openpt - open a pseudo terminal device
SYNOPSIS
#include <stdlib.h>
#include <fcntl.h>
int posix_openpt(int oflag);
DESCRIPTION
The posix_openpt() 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.
The file status flags and file access modes of the open file descrip‐
tion are set according to the value of oflag.
Values for oflag are constructed by a bitwise-inclusive OR of flags
from the following list, defined in <fcntl.h>.
O_RDWR
Open for reading and writing.
O_NOCTTY
If set, posix_openpt() does not cause the terminal device
to become the controlling terminal for the process.
The behavior of other values for the oflag argument is unspecified.
RETURN VALUES
Upon successful completion, the posix_openpt() 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 errno is set to indicate the error.
ERRORS
The posix_openpt() function will fail if:
EMFILE
{OPEN_MAX} file descriptors are currently open in the calling
process.
ENFILE
The maximum allowable number of files is currently open in
the system.
The posix_openpt() function may fail if:
EINVAL
The value of oflag is not valid.
EAGAIN
Out of pseudo-terminal resources.
ENOSR
Out of STREAMS resources.
EXAMPLES
Example 1 Open a pseudo-terminal.
The following example opens a pseudo-terminal and returns the name of
the slave device and a file descriptor.
#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\n", slavedevice);
slavefd = open(slave, O_RDWR|O_NOCTTY);
if (slavefd < 0)
return -1;
USAGE
This function provides a method for portably obtaining a file descrip‐
tor of a master terminal device for a pseudo-terminal. The grantpt(3C)
and ptsname(3C) functions can be used to manipulate mode and ownership
permissions and to obtain the name of the slave device, respectively.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
├────────────────────┼─────────────────┤
│MT-Level │ MT-Safe │
└────────────────────┴─────────────────┘
SEE ALSOopen(2), grantpt(3C), ptsname(3C), unlockpt(3C), attributes(5), stan‐
dards(5)
Dec 1, 2003 POSIX_OPENPT(3C)
