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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON |
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OPENPTY(3) Linux Programmer's Manual OPENPTY(3)
openpty, login_tty, forkpty - terminal utility functions
#include <pty.h>
int openpty(int *amaster, int *aslave, char *name,
const struct termios *termp,
const struct winsize *winp);
pid_t forkpty(int *amaster, char *name,
const struct termios *termp,
const struct winsize *winp);
#include <utmp.h>
int login_tty(int fd);
Link with -lutil.
The openpty() function finds an available pseudoterminal and
returns file descriptors for the master and slave in amaster and
aslave. If name is not NULL, the filename of the slave is
returned in name. If termp is not NULL, the terminal parameters
of the slave will be set to the values in termp. If winp is not
NULL, the window size of the slave will be set to the values in
winp.
The login_tty() function prepares for a login on the terminal
referred to by the file descriptor fd (which may be a real
terminal device, or the slave of a pseudoterminal as returned by
openpty()) by creating a new session, making fd the controlling
terminal for the calling process, setting fd to be the standard
input, output, and error streams of the current process, and
closing fd.
The forkpty() function combines openpty(), fork(2), and
login_tty() to create a new process operating in a
pseudoterminal. A file descriptor referring to master side of
the pseudoterminal is returned in amaster. If name is not NULL,
the buffer it points to is used to return the filename of the
slave. The termp and winp arguments, if not NULL, will determine
the terminal attributes and window size of the slave side of the
pseudoterminal.
If a call to openpty(), login_tty(), or forkpty() is not
successful, -1 is returned and errno is set to indicate the
error. Otherwise, openpty(), login_tty(), and the child process
of forkpty() return 0, and the parent process of forkpty()
returns the process ID of the child process.
openpty() fails if:
ENOENT There are no available terminals.
login_tty() fails if ioctl(2) fails to set fd to the controlling
terminal of the calling process.
forkpty() fails if either openpty() or fork(2) fails.
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────┬───────────────┬────────────────────────┐
│Interface │ Attribute │ Value │
├─────────────────────┼───────────────┼────────────────────────┤
│forkpty(), openpty() │ Thread safety │ MT-Safe locale │
├─────────────────────┼───────────────┼────────────────────────┤
│login_tty() │ Thread safety │ MT-Unsafe race:ttyname │
└─────────────────────┴───────────────┴────────────────────────┘
These are BSD functions, present in glibc. They are not
standardized in POSIX.
The const modifiers were added to the structure pointer arguments
of openpty() and forkpty() in glibc 2.8.
In versions of glibc before 2.0.92, openpty() returns file
descriptors for a BSD pseudoterminal pair; since glibc 2.0.92, it
first attempts to open a UNIX 98 pseudoterminal pair, and falls
back to opening a BSD pseudoterminal pair if that fails.
Nobody knows how much space should be reserved for name. So,
calling openpty() or forkpty() with non-NULL name may not be
secure.
fork(2), ttyname(3), pty(7)
This page is part of release 5.10 of the Linux man-pages project.
A description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2017-09-15 OPENPTY(3)
Pages that refer to this page: pty(7)
Copyright and license for this manual page
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