Originální popis anglicky:
posix_openpt - open a pseudo-terminal device
Návod, kniha: POSIX Programmer's Manual
#include <stdlib.h>
#include <fcntl.h>
int posix_openpt(int
oflag);
The
posix_openpt() function shall establish 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 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.
The behavior of other values for the
oflag argument is unspecified.
Upon successful completion, the
posix_openpt() function shall open a
master pseudo-terminal device and return a non-negative integer representing
the lowest numbered unused file descriptor. Otherwise, -1 shall be returned
and
errno set to indicate the error.
The
posix_openpt() function shall 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.
The following sections are informative.
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;
This function is a method for portably obtaining a file descriptor of a master
terminal device for a pseudo-terminal. The
grantpt() and
ptsname() functions can be used to manipulate mode and ownership
permissions, and to obtain the name of the slave device, respectively.
The standard developers considered the matter of adding a special device for
cloning master pseudo-terminals: the
/dev/ptmx device. However,
consensus could not be reached, and it was felt that adding a new function
would permit other implementations. The
posix_openpt() function is
designed to complement the
grantpt(),
ptsname(), and
unlockpt() functions.
On implementations supporting the
/dev/ptmx clone device, opening the
master device of a pseudo-terminal is simply:
mfdp = open("/dev/ptmx", oflag );
if (mfdp < 0)
return -1;
None.
grantpt() ,
open() ,
ptsname() ,
unlockpt() , the
Base Definitions volume of IEEE Std 1003.1-2001,
<fcntl.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
