1  /* Copyright (C) 1991-2023 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.  */
      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  }