Manpage of OPENPTY

OPENPTY

Section: Linux Programmer's Manual (3)
Updated: 2015-04-19
Index
 

NAME

openpty, login_tty, forkpty - terminal utility functions  

SYNOPSIS

#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.
 

DESCRIPTION

The openpty() function finds an available pseudoterminal and returns file descriptors for the master and slave in amasterand aslave. If nameis not NULL, the filename of the slave is returned in name. If termpis not NULL, the terminal parameters of the slave will be set to the values in termp. If winpis 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 fd(which may be a real terminal device, or the slave of a pseudoterminal as returned by openpty()) by creating a new session, making fdthe controlling terminal for the calling process, setting fdto 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. The file descriptor of the master side of the pseudoterminal is returned in amaster, and the filename of the slave in nameif it is not NULL. The termpand winparguments, if not NULL, will determine the terminal attributes and window size of the slave side of the pseudoterminal.  

RETURN VALUE

If a call to openpty(), login_tty(), or forkpty() is not successful, -1 is returned and errnois 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.  

ERRORS

openpty() will fail if:
ENOENT
There are no available terminals.

login_tty() will fail if ioctl(2) fails to set fdto the controlling terminal of the calling process.

forkpty() will fail if either openpty() or fork(2) fails.  

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
forkpty(), openpty() Thread safetyMT-Safe locale
login_tty() Thread safetyMT-Unsafe race:ttyname

 

CONFORMING TO

These are BSD functions, present in glibc. They are not standardized in POSIX.  

NOTES

The constmodifiers 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.  

BUGS

Nobody knows how much space should be reserved for name. So, calling openpty() or forkpty() with non-NULL namemay not be secure.  

SEE ALSO

fork(2), ttyname(3), pty(7)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
NOTES
BUGS
SEE ALSO

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Time: 22:27:45 GMT, June 20, 2016