#include <stdlib.h> int grantpt(int fildes);
The grantpt() function changes the mode and ownership of the slave pseudo-terminal device associated with its master pseudo-terminal counterpart. fildes is the file descriptor returned from a successful open of the master pseudo-terminal device. The user ID of the slave is set to the real UID of the calling process and the group ID is set to a reserved group. The permission mode of the slave pseudo-terminal is set to readable and writable by the owner and writable by the group.
Upon successful completion, grantpt() returns 0. Otherwise, it returns −1 and sets errno to indicate the error.
The grantpt() function may fail if:
The fildes argument is not a valid open file descriptor.
The fildes argument is not associated with a master pseudo-terminal device.
The corresponding slave pseudo-terminal device could not be accessed.
See attributes(5) for descriptions of the following attributes: