sysdeps/posix/cuserid.c

   1 /* Copyright (C) 1991-2016 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    <http://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.  */
  27 char *
  28 cuserid (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 }