POSIX_OPENPT(2) BSD System Calls Manual POSIX_OPENPT(2)NAME
posix_openpt -- open a pseudo-terminal device
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdlib.h>
#include <fcntl.h>
int
posix_openpt(int oflag);
DESCRIPTION
The posix_openpt() function allocates a new pseudo-terminal and establishes a connection with its master device. A slave device shall be
created in /dev/pts. After the pseudo-terminal has been allocated, the slave device should have the proper permissions before it can be used
(see grantpt(3)). The name of the slave device can be determined by calling ptsname(3).
The file status flags and file access modes of the open file description shall be 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() shall not cause the terminal device to become the controlling terminal for the process.
O_CLOEXEC Set the close-on-exec flag for the new file descriptor.
The posix_openpt() function shall fail when oflag contains other values.
RETURN VALUES
Upon successful completion, the posix_openpt() function shall allocate a new pseudo-terminal device and return a non-negative integer repre-
senting a file descriptor, which is connected to its master device. Otherwise, -1 shall be returned and errno set to indicate the error.
ERRORS
The posix_openpt() function shall fail if:
[ENFILE] The system file table is full.
[EINVAL] The value of oflag is not valid.
[EAGAIN] Out of pseudo-terminal resources.
SEE ALSO ptsname(3), pts(4), tty(4)STANDARDS
The posix_openpt() function conforms to IEEE Std 1003.1-2001 (``POSIX.1''). The ability to use O_CLOEXEC is an extension to the standard.
HISTORY
The posix_openpt() function appeared in FreeBSD 5.0. In FreeBSD 8.0, this function was changed to a system call.
NOTES
The flag O_NOCTTY is included for compatibility; in FreeBSD, opening a terminal does not cause it to become a process's controlling terminal.
AUTHORS
Ed Schouten <ed@FreeBSD.org>
BSD March 21, 2013 BSD
Check Out this Related Man Page
GRANTPT(3) BSD Library Functions Manual GRANTPT(3)NAME
grantpt, posix_openpt, ptsname, ptsname_r, unlockpt -- pseudo-terminal access functions
SYNOPSIS
#include <stdlib.h>
int
grantpt(int fildes);
char *
ptsname(int fildes);
int
ptsname_r(int fildes, char *buffer, size_t buflen);
int
unlockpt(int fildes);
#include <stdlib.h>
#include <fcntl.h>
int
posix_openpt(int oflag);
DESCRIPTION
The grantpt(), ptsname(), ptsname_r(), unlockpt(), and posix_openpt() functions allow access to pseudo-terminal devices. The first four
functions accept a file descriptor that references the master half of a pseudo-terminal pair. This file descriptor is created with
posix_openpt().
The grantpt() function is used to establish ownership and permissions of the slave device counterpart to the master device specified with
fildes. The slave device's ownership is set to the real user ID of the calling process; its permissions are set to user readable-writable
and group writable. The group owner of the slave device is also set to the group ``tty'' if it exists on the system; otherwise, it is left
untouched.
The ptsname() and ptsname_r() functions return the full pathname of the slave device counterpart to the master device specified with fildes.
This value can be used to subsequently open the appropriate slave after posix_openpt() and grantpt() have been called. The ptsname() function
is not guaranteed to be reentrant or thread safe. The ptsname_r() function takes a buffer and length as arguments to avoid this problem.
The unlockpt() function unlocks the slave pseudo-terminal device associated with the master device to which fildes refers.
The posix_openpt() function opens the first available master pseudo-terminal device and returns a descriptor to it. The oflag argument spec-
ifies the flags used for opening the device:
O_RDWR Open for reading and writing.
O_NOCTTY If set, do not allow the terminal to become the controlling terminal for the calling process.
RETURN VALUES
The grantpt() and unlockpt() functions return the value 0 if successful; otherwise the value -1 is returned and the global variable errno is
set to indicate the error.
The ptsname() function returns a pointer to the name of the slave device on success; otherwise a NULL pointer is returned and the global
variable errno is set to indicate the error.
The ptsname_r() function returns 0 if successful. On failure, it returns -1 and the global variable errno is set to indicate the error.
The posix_openpt() function returns a file descriptor to the first available master pseudo-terminal device on success; otherwise -1 is
returned and the global variable errno is set to indicate the error.
ERRORS
The grantpt(), ptsname(), ptsname_r(), and unlockpt() functions may fail and set errno to:
[EINVAL] fildes is not a master pseudo-terminal device.
In addition, the ptsname_r() function may set errno to:
[EINVAL] The buffer argument is NULL.
[ERANGE] The bufsize argument is smaller than the length of the string to be returned.
In addition, the grantpt() function may set errno to:
[EACCES] The slave pseudo-terminal device could not be accessed.
The posix_openpt() function may fail and set errno to:
[EINVAL] oflag consists of an invalid mode bit.
[EAGAIN] The system has no available pseudo-terminal devices.
The grantpt(), ptsname(), ptsname_r(), and unlockpt() functions may also fail and set errno for any of the errors specified for the fstat(2)
system call.
The posix_openpt() function may also fail and set errno for any of the errors specified for the open(2) system call.
LEGACY SYNOPSIS
#include <stdlib.h>
#include <fcntl.h>
int
grantpt(int fildes);
char *
ptsname(int fildes);
int
unlockpt(int fildes);
#include <fcntl.h>
int
posix_openpt(int oflag);
SEE ALSO open(2), pty(4), tty(4), compat(5)STANDARDS
The grantpt(), ptsname(), unlockpt(), and posix_openpt() functions conform to IEEE Std 1003.1-2001 (``POSIX.1'').
BSD February 2, 2005 BSD