getgrent(3) — Linux manual page


getgrent(3)             Library Functions Manual             getgrent(3)

NAME         top

       getgrent, setgrent, endgrent - get group file entry

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

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

       struct group *getgrent(void);

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

   Feature Test Macro Requirements for glibc (see

           _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         top

       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

RETURN VALUE         top

       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         top

       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

       ENOMEM Insufficient memory to allocate group structure.

       ERANGE Insufficient buffer space supplied.

FILES         top

              local group database file

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ 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

STANDARDS         top


HISTORY         top

       POSIX.1-2001, SVr4, 4.3BSD.

SEE ALSO         top

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

Linux man-pages (unreleased)     (date)                      getgrent(3)

Pages that refer to this page: getent(1)pmcd(1)pmdapipe(1)fgetgrent(3)getgrent_r(3)getgrnam(3)getgrouplist(3)putgrent(3)setaliasent(3)group(5)nss(5)nsswitch.conf(5)