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(), 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.

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)