Manpage of GRANTPT
GRANTPTSection: Linux Programmer's Manual (3)
NAMEgrantpt - grant access to the slave pseudoterminal
int grantpt(int fd);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
- Since glibc 2.24:
_XOPEN_SOURCE >= 500 ||
(_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED)
Glibc 2.23 and earlier:
DESCRIPTIONThe grantpt() function changes the mode and owner of the slave pseudoterminal device corresponding to the master pseudoterminal referred to by fd. The user ID of the slave is set to the real UID of the calling process. The group ID is set to an unspecified value (e.g., tty). The mode of the slave is set to 0620 (crw--w----).
RETURN VALUEWhen successful, grantpt() returns 0. Otherwise, it returns -1 and sets errnoappropriately.
- The corresponding slave pseudoterminal could not be accessed.
- The fdargument is not a valid open file descriptor.
- The fdargument is valid but not associated with a master pseudoterminal.
VERSIONSgrantpt() is provided in glibc since version 2.1.
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
|grantpt()||Thread safety||MT-Safe locale|
CONFORMING TOPOSIX.1-2001, POSIX.1-2008.
NOTESThis is part of the UNIX 98 pseudoterminal support, see pts(4).
Many systems implement this function via a set-user-ID helper binary called "pt_chown". On Linux systems with a devpts filesystem (present since Linux 2.2), the kernel normally sets the correct ownership and permissions for the pseudoterminal slave when the master is opened (posix_openpt(3)), so that nothing must be done by grantpt(). Thus, no such helper binary is required (and indeed it is configured to be absent during the glibc build that is typical on many systems).
SEE ALSOopen(2), posix_openpt(3), ptsname(3), unlockpt(3), pts(4), pty(7)
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