grantpt - Man Page

grant access to the slave pseudo-terminal device


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


#include <stdlib.h>

int grantpt(int fildes);


The grantpt() function shall change the mode and ownership of the slave pseudo-terminal device associated with its master pseudo-terminal counterpart. The fildes argument is a file descriptor that refers to a master pseudo-terminal device. The user ID of the slave shall be set to the real UID of the calling process and the group ID shall be set to an unspecified group ID. The permission mode of the slave pseudo-terminal shall be set to readable and writable by the owner, and writable by the group.

The behavior of the grantpt() function is unspecified if the application has installed a signal handler to catch SIGCHLD signals.

Return Value

Upon successful completion, grantpt() shall return 0; otherwise, it shall return -1 and set errno to indicate the error.


The grantpt() function may fail if:


The corresponding slave pseudo-terminal device could not be accessed.


The fildes argument is not a valid open file descriptor.


The fildes argument is not associated with a master pseudo-terminal device.

The following sections are informative.



Application Usage



See the RATIONALE section for posix_openpt().

Future Directions


See Also

open(), posix_openpt(), ptsname(), unlockpt()

The Base Definitions volume of POSIX.1-2017, <stdlib.h>

Referenced By

posix_openpt(3p), ptsname(3p), stdlib.h(0p), unlockpt(3p).

2017 IEEE/The Open Group POSIX Programmer's Manual