getgrent(3)                Library Functions Manual                getgrent(3)

NAME
       getgrent, setgrent, endgrent - get group file entry

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #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)):

       setgrent():
           _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

DESCRIPTION
       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).

RETURN VALUE
       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 getgrnam(3).  (Do not
       pass the returned pointer to free(3).)

ERRORS
       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 configured.

       ENOMEM Insufficient memory to allocate group structure.

       ERANGE Insufficient buffer space supplied.

FILES
       /etc/group
              local group database file

ATTRIBUTES
       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 (), | Thread safety | MT-Unsafe race:grent locale            |
       |endgrent ()  |               |                                        |
       +-------------+---------------+----------------------------------------+
       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.

STANDARDS
       POSIX.1-2008.

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

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

Linux man-pages 6.7               2023-10-31                       getgrent(3)