1/* Copyright (C) 1991-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <pwd.h>
19#include <stdio.h>
20#include <string.h>
21#include <unistd.h>
22#include <sys/types.h>
23
24/* Return the username of the caller.
25 If S is not NULL, it points to a buffer of at least L_cuserid bytes
26 into which the name is copied; otherwise, a static buffer is used. */
27char *
28cuserid (char *s)
29{
30 static char name[L_cuserid];
31 char buf[NSS_BUFLEN_PASSWD];
32 struct passwd pwent;
33 struct passwd *pwptr;
34
35 if (__getpwuid_r (__geteuid (), &pwent, buf, sizeof (buf), &pwptr)
36 || pwptr == NULL)
37 {
38 if (s != NULL)
39 s[0] = '\0';
40 return s;
41 }
42
43 if (s == NULL)
44 s = name;
45 s[L_cuserid - 1] = '\0';
46 return strncpy (s, pwptr->pw_name, L_cuserid - 1);
47}
48

source code of glibc/sysdeps/posix/cuserid.c