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GRANTPT(3) BSD Library Functions Manual GRANTPT(3) NAME grantpt, ptsname, unlockpt, posix_openpt -- pseudo-terminal access func- tions LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <stdlib.h> int grantpt(int fildes); char * ptsname(int fildes); int unlockpt(int fildes); #include <fcntl.h> int posix_openpt(int mode); DESCRIPTION The grantpt(), ptsname(), unlockpt(), and posix_openpt() functions allow access to pseudo-terminal devices. The first three 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, and the 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() function returns 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 unlockpt() function clears the lock held on the pseudo-terminal pair for the master device specified with fildes. The posix_openpt() function opens the first available master pseudo-ter- minal device and returns a descriptor to it. The mode argument specifies 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 posix_openpt() function returns a file descriptor to the first avail- able 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(), and unlockpt() functions may fail and set errno to: [EINVAL] fildes is not a master pseudo-terminal device. In addition, the grantpt() function may set errno to: [EACCES] The slave pseudo-terminal device could not be ac- cessed. The posix_openpt() function may fail and set errno to: [EINVAL] mode consists of an invalid mode bit. [EAGAIN] The system has no available pseudo-terminal devices. The grantpt(), ptsname(), 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. SEE ALSO open(2), pty(4), tty(4) STANDARDS The grantpt(), ptsname(), unlockpt(), and posix_openpt() functions con- form to IEEE Std 1003.1-2001 ("POSIX.1"). HISTORY The grantpt(), ptsname(), unlockpt(), and posix_openpt() functions ap- peared in FreeBSD 5.0. NOTES The purpose of the unlockpt() function has no meaning in FreeBSD. The flag O_NOCTTY is included for compatibility; in FreeBSD, opening a terminal does not cause it to become a process's controlling terminal. BSD December 23, 2002 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY | NOTES
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