getgid (2) - Linux Man Pages
getgid: get group identity
getgid, getegid - get group identity
DESCRIPTIONgetgid() returns the real group ID of the calling process.
ERRORSThese functions are always successful.
CONFORMING TOPOSIX.1-2001, POSIX.1-2008, 4.3BSD.
NOTESThe original Linux getgid() and getegid() system calls supported only 16-bit group IDs. Subsequently, Linux 2.4 added getgid32() and getegid32(), supporting 32-bit IDs. The glibc getgid() and getegid() wrapper functions transparently deal with the variations across kernel versions.
On Alpha, instead of a pair of getgid() and getegid() system calls, a single getxgid() system call is provided, which returns a pair of real and effective GIDs. The glibc getgid() and getegid() wrapper functions transparently deal with this. See syscall(2) for details regarding register mapping.
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