apps/utils/whoami.c

   1 /*
   2     meinOS - A unix-like x86 microkernel operating system
   3     Copyright (C) 2008  Janosch Gräf <janosch.graef@gmx.net>
   4
   5     This program is free software: you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation, either version 3 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License
  16     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19 #include <pwd.h>
  20 #include <unistd.h>
  21 #include <stdio.h>
  22
  23 static void usage(char *cmd,int ret) {
  24   FILE *stream = ret==0?stdout:stderr;
  25   fprintf(stream,"Usage: %s [OPTION]... [STRING]...\n");
  26   fprintf(stream,"Print effective UID\n");
  27   fprintf(stream,"\t-h\tshow this help message\n");
  28   fprintf(stream,"\t-v\toutput version information and exit\n");
  29 }
  30
  31 int main(int argc,char *argv[]) {
  32   int c;
  33
  34   while ((c = getopt(argc,argv,":hv"))!=-1) {
  35     switch(c) {
  36       case 'h':
  37         usage(argv[0],0);
  38         break;
  39       case 'v':
  40         printf("whoami v0.1\n(c) 2008 Janosch Graef\n");
  41         return 0;
  42         break;
  43       case '?':
  44         fprintf(stderr,"Unrecognized option: -%c\n", optopt);
  45         usage(argv[0],1);
  46         break;
  47     }
  48   }
  49
  50   struct passwd *pwd = getpwuid(geteuid());
  51   if (pwd==NULL) {
  52     perror("getpwuid");
  53     return 1;
  54   }
  55
  56   puts(pwd->pw_name);
  57
  58   return 0;
  59 }