getgrent

GETGRENT(3)                Linux Programmer's Manual               GETGRENT(3)



NAME
       getgrent, setgrent, endgrent - get group file entry

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():
           _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED ||
           /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L

       getgrent(), endgrent():
           _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

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;        /* 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
       EINTR  A signal was caught.

       EIO    I/O error.

       EMFILE The calling process already has too many open files.

       ENFILE Too many open files in the system.

       ENOMEM Insufficient memory to allocate group structure.

       ERANGE Insufficient buffer space supplied.

FILES
       /etc/group
              local group database file

ATTRIBUTES
   Multithreading (see pthreads(7))
       The getgrent() function is not thread-safe.

       The setgrent() and endgrent() functions are thread-safe.

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.  ]]

CONFORMING TO
       SVr4, 4.3BSD, POSIX.1-2001.

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

COLOPHON
       This page is part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



                                  2013-06-21                       GETGRENT(3)