Manpage of OPENPTY
OPENPTYSection: Linux Programmer's Manual (3)
NAMEopenpty, 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.
DESCRIPTIONThe 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 VALUEIf 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.
ERRORSopenpty() will fail if:
- 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.
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
|forkpty(), openpty()||Thread safety||MT-Safe locale|
|login_tty()||Thread safety||MT-Unsafe race:ttyname|
CONFORMING TOThese are BSD functions, present in glibc. They are not standardized in POSIX.
NOTESThe 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.
BUGSNobody knows how much space should be reserved for name. So, calling openpty() or forkpty() with non-NULL namemay not be secure.
SEE ALSOfork(2), ttyname(3), pty(7)
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