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       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

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

       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 getgrnam(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 configured.

       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).

       │InterfaceAttributeValue                                           │
       │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),