.\" Copyright (C) 2014, Michael Kerrisk .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .TH group_member 3 2024-05-02 "Linux man-pages 6.8" .SH NAME group_member \- test whether a process is in a group .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .P .BI "int group_member(gid_t " gid ); .fi .P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .P .BR group_member (): .nf _GNU_SOURCE .fi .SH DESCRIPTION The .BR group_member () function tests whether any of the caller's supplementary group IDs (as returned by .BR getgroups (2)) matches .IR gid . .SH RETURN VALUE The .BR group_member () function returns nonzero if any of the caller's supplementary group IDs matches .IR gid , and zero otherwise. .SH STANDARDS GNU. .SH SEE ALSO .BR getgid (2), .BR getgroups (2), .BR getgrouplist (3), .BR group (5)