FGETGRENT(3) Linux Programmer's Manual FGETGRENT(3)

fgetgrent - get group file entry

#include <stdio.h>
#include <sys/types.h>
#include <grp.h>
struct group *fgetgrent(FILE *stream);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
fgetgrent():
Since glibc 2.19:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_SVID_SOURCE

The fgetgrent() function returns a pointer to a structure containing the group information from the file referred to by stream. The first time it is called it returns the first entry; thereafter, it returns successive entries. The file referred to by stream must have the same format as /etc/group (see group(5)).
The group structure is defined in <grp.h> as follows:

struct group {
    char   *gr_name;        /* group name */
    char   *gr_passwd;      /* group password */
    gid_t   gr_gid;         /* group ID */
    char  **gr_mem;         /* NULL-terminated array of pointers
                               to names of group members */
};

The fgetgrent() function returns a pointer to a group structure, or NULL if there are no more entries or an error occurs. In the event of an error, errno is set to indicate the cause.

ENOMEM
Insufficient memory to allocate group structure.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
fgetgrent () Thread safety MT-Unsafe race:fgetgrent

SVr4.

endgrent(3), fgetgrent_r(3), fopen(3), getgrent(3), getgrgid(3), getgrnam(3), putgrent(3), setgrent(3), group(5)
2017-09-15 GNU