// whoami.c - a simple implementation of whoami utility
// This code was sourced from http://www.gnu.org/software/cflow/manual/cflow.html
 
#include <pwd.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
     
int  who_am_i(void) {
          
          struct passwd *pw;
          char *user = NULL;

          pw = getpwuid(geteuid());
          if (pw)
               user = pw->pw_name;
          else if ((user = getenv("USER")) == NULL) {
               fprintf(stderr, "I don't know!\n");
               return 1;
          }
          printf("%s\n", user);
          return 0;
}

     
int  main (int argc, char **argv)
{
          
    if (argc > 1) {
       fprintf (stderr, "usage: whoami\n");
       return 1;
    }
          
    return who_am_i ();
          
}