getgrent(3)                                           Library Functions Manual                                          getgrent(3)

       getgrent, setgrent, endgrent - get group file entry

       Standard C library (libc, -lc)

       #include <sys/types.h>
       #include <grp.h>

       struct group *getgrent(void);

       void setgrent(void);
       void endgrent(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           _XOPEN_SOURCE >= 500
               || /* glibc >= 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       getgrent(), endgrent():
           Since glibc 2.22:
               _XOPEN_SOURCE >= 500 || _DEFAULT_SOURCE
           glibc 2.21 and earlier
               _XOPEN_SOURCE >= 500
                   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
                   || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       The  getgrent() function returns a pointer to a structure containing the broken-out fields of a record in the group database
       (e.g., the local group file /etc/group, NIS, and LDAP).  The first time getgrent() is called, it returns  the  first  entry;
       thereafter, it returns successive entries.

       The setgrent() function rewinds to the beginning of the group database, to allow repeated scans.

       The endgrent() function is used to close the group database after all processing has been performed.

       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 */

       For more information about the fields of this structure, see group(5).

       The getgrent() function returns a pointer to a group structure, or NULL if there are no more entries or an error occurs.

       Upon error, errno may be set.  If one wants to check errno after the call, it should be set to zero before the call.

       The  return value may point to a static area, and may be overwritten by subsequent calls to getgrent(), getgrgid(3), or get‐
       grnam(3).  (Do not pass the returned pointer to free(3).)

       EAGAIN The service was temporarily unavailable; try again later.  For NSS backends in glibc this indicates a temporary error
              talking to the backend.  The error may correct itself, retrying later is suggested.

       EINTR  A signal was caught; see signal(7).

       EIO    I/O error.

       EMFILE The per-process limit on the number of open file descriptors has been reached.

       ENFILE The system-wide limit on the total number of open files has been reached.

       ENOENT A  necessary  input file cannot be found.  For NSS backends in glibc this indicates the backend is not correctly con‐

       ENOMEM Insufficient memory to allocate group structure.

       ERANGE Insufficient buffer space supplied.

              local group database file

       For an explanation of the terms used in this section, see attributes(7).

       │Interface              │ Attribute     │ Value                                                                             │
       │getgrent()             │ Thread safety │ MT-Unsafe race:grent race:grentbuf locale                                         │
       │setgrent(), endgrent() │ Thread safety │ MT-Unsafe race:grent locale                                                       │

       In the above table, grent in race:grent signifies that if any of the functions setgrent(),  getgrent(),  or  endgrent()  are
       used in parallel in different threads of a program, then data races could occur.

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

       fgetgrent(3), getgrent_r(3), getgrgid(3), getgrnam(3), getgrouplist(3), putgrent(3), group(5)

Linux man-pages 6.03                                         2023-02-05                                                 getgrent(3)