getpwXXX.c

/**
   @file      getpwXXX.c
   @author    Mitch Richling <http://www.mitchr.me/>
   @Copyright Copyright 1996 by Mitch Richling.  All rights reserved.
   @brief     UNIX password lookup @EOL
   @Keywords  UNIX password shadow passwd getpwnam getpwuid
   @Std       ISOC POSIX UNIX98 BSD4.3 SYSV3

              This is an example program intended to illustrate how to
              query most UNIX versions for password information by
              user name (uname) or user ID (UID).

   @Tested    
              - Solaris 2.8
              - MacOS X.2
              - Linux (RH 7.3)
*/

#include <pwd.h>                /* UNIX passwd     POSIX */
#include <sys/types.h>          /* UNIX types      POSIX */
#include <stdlib.h>             /* Standard Lib    ISOC  */
#include <unistd.h>             /* UNIX std stf    POSIX */
#include <stdio.h>              /* I/O lib         ISOC  */
#include <ctype.h>              /* Char classes    ISOC  */

int main(int argc, char *argv[]);

int main(int argc, char *argv[]) {
  struct passwd *pwEnt;
  char *c;
  uid_t theUID;
  int ArgIsNotNumber;

  if(argc != 2) {
    printf("ERROR: This program requires a user name or UID as the only argument.\n");
    exit(1);
  } /* end if */

  /* Figure out if we got a user name or a UID */
  for(c=argv[1],ArgIsNotNumber=0;!((*c=='\0')||ArgIsNotNumber);c++)
    if(!isdigit(*c))
      ArgIsNotNumber=1;

  /* Do the lookup */
  if(ArgIsNotNumber) {
    printf("Looking up user with user name: %s...\n\n", argv[1]);
    if( (pwEnt = getpwnam(argv[1])) == NULL) {
      printf("ERROR: Call to getpwnam failed.\n");
      exit(1);
    } /* end if */
  } else {
    theUID = atol(argv[1]);
    printf("Looking up user with UID: %ld...\n\n", (long)theUID);
    if((pwEnt = getpwuid(theUID)) == NULL) {
      printf("ERROR: Call to getpwuid failed.\n");
      exit(2);
    } /* end if */
  } /* end if/else */

  printf("pw_name:   %s\n",  pwEnt->pw_name);
  printf("pw_passwd: %s\n",  pwEnt->pw_passwd);
  printf("pw_uid:    %ld\n", (long)pwEnt->pw_uid);
  printf("pw_gid:    %ld\n", (long)pwEnt->pw_gid);
  printf("pw_gecos:  %s\n",  pwEnt->pw_gecos);
  printf("pw_dir:    %s\n",  pwEnt->pw_dir);
  printf("pw_shell:  %s\n",  pwEnt->pw_shell);

  return 0;
} /* end func main */