putgrent — write a group database entry to a file
#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <grp.h>
| int
            putgrent( | const struct group *grp, | 
| FILE *fp ); | 
The putgrent() function is
      the counterpart for fgetgrent(3). The function
      writes the content of the provided struct group into the file pointed
      to by fp. The list of
      group members must be NULL-terminated or
      NULL-initialized.
The struct group is defined as follows:
struct group { char * gr_name;char * gr_passwd;gid_t gr_gid;char ** gr_mem;};