getgrent()

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The getgrent() function returns the next entry from the group database, although no particular order is guaranteed. This function uses a static buffer that's overwritten by each call.

Returns:

The next entry from the group database. When you first call getgrent(), the group database is opened. It remains open until either getgrent() returns NULL to signify end-of-file, or you call endgrent().

Errors:

The getgrent() function uses the following functions, and as a result, errno can be set to an error for any of these calls:

• fclose()
• fgets()
• fopen()
• fseek()
• rewind()

Examples:

/*
 * This program loops, reading a group name from standard input
 * and checking to see if it is a valid group. If it isn't valid,
 * the entire contents of the group database are printed.
 */
#include <stdio.h>
#include <stdlib.h>
#include <grp.h>
#include <limits.h>

int main( void )
{
  struct group* gr;
  char    buf[80];

  setgrent();
  while( gets(buf) != NULL) {
    if( (gr=getgrnam(buf)) != (struct group *)0) {
      printf("Valid group is: %s\n",gr->gr_name);
    } else {
      setgrent();
      while( (gr=getgrent()) != (struct group *)0 )
        printf("%s\n",gr->gr_name);
    }
  }
  endgrent();
  return( EXIT_SUCCESS );
}

Classification:

POSIX 1003.1