GETGRENT(3)              BSD Library Functions Manual              GETGRENT(3)

NAME
     getgrent, getgrnam, getgrnam_r, getgrgid, getgrgid_r, getgruuid,
     getgruuid_r, setgroupent, setgrent, endgrent -- group database operations

LIBRARY
     Standard system libraries.

SYNOPSIS
     #include <grp.h>
     #include <uuid/uuid.h>

     struct group *
     getgrent(void);

     struct group *
     getgrnam(const char *name);

     int
     getgrnam_r(const char *name, struct group *grp, char *buffer,
         size_t bufsize, struct group **result);

     struct group *
     getgrgid(gid_t gid);

     int
     getgrgid_r(gid_t gid, struct group *grp, char *buffer, size_t bufsize,
         struct group **result);

     int
     getgruuid(uuid_t uuid);

     int
     getgruuid_r(uuid_t uuid, struct group *grp, char *buffer, size_t bufsize,
         struct group **result);

     int
     setgroupent(int stayopen);

     void
     setgrent(void);

     void
     endgrent(void);

DESCRIPTION
     These functions obtain information from opendirectoryd(8), including
     records in /etc/group which is described in group(5).  Each line of the
     database is defined by the structure group found in the include file
     <grp.h>:

           struct group {
                   char    *gr_name;       /* group name */
                   char    *gr_passwd;     /* group password */
                   gid_t   gr_gid;         /* group id */
                   char    **gr_mem;       /* group members */
           };

     The functions getgrnam(), getgrgid(), and getgruuid() search the group
     database for the given group name pointed to by name, the group id given
     by gid, or the UUID given by uuid respectively, returning the first one
     encountered.  Identical group names, group gids, or uuids may result in
     undefined behavior.

     Note that the groups file /etc/group does not contain group UUIDs.  The
     UUID for a group may be found using mbr_gid_to_uuid().

     On OS X, these routines are thread-safe and return a pointer to a thread-
     specific data structure.  The contents of this data structure are auto-
     matically released by subsequent calls to any of these routines on the
     same thread, or when the thread exits.  These routines are therefore
     unsuitable for use in libraries or frameworks, from where they may over-
     write the per-thread data that the calling application expects to find as
     a result of its own calls to these routines. Library and framework code
     should use the alternative reentrant variants detailed below.

     The getgrent() function searches all available directory services on it's
     first invocation.  It caches the returned entries in a list and returns
     group entries one at a time.

     NOTE that getgrent() may cause a very lengthy search for group records by
     opendirectoryd and may result in a large number of group records being
     cached by the calling process.  Use of this function is not advised.

     The functions getgrnam_r(), getgrgid_r(), and getgruuid_r() are alterna-
     tive versions of getgrnam(), getgrgid(), and getgruuid() respectively.
     The caller must provide storage for the results of the search in the grp,
     buffer, bufsize, and result arguments.  When these functions are success-
     ful, the grp argument will be filled-in, and a pointer to that argument
     will be stored in result.  If an entry is not found or an error occurs,
     result will be set to NULL.

     These functions will open the group file for reading, if necessary.

     The setgroupent() function causes getgrent() to ``rewind'' to the begin-
     ning of the list of entries cached by a previous getgrent() call.  The
     cache is not cleared.  The stayopen parameter value is unused on OS X.

     The setgrent() and endgrent() functions clear the cached results from a
     previous getgrent() call.

RETURN VALUES
     The functions getgrent(), getgrnam(), and getgrgid(), return a pointer to
     a group structure on success or NULL if the entry is not found or if an
     error occurs.  If an error does occur, errno will be set.  Note that pro-
     grams must explicitly set errno to zero before calling any of these func-
     tions if they need to distinguish between a non-existent entry and an
     error.  The functions getgrnam_r(), getgrgid_r(), and getgruuid_r()
     return 0 if no error occurred, or an error number to indicate failure.
     It is not an error if a matching entry is not found.  (Thus, if result is
     set to NULL and the return value is 0, no matching entry exists.)

     setgroupent() returns the value 1 if successful, otherwise the value 0 is
     returned.  The functions setgrent(), endgrent(), and setgrfile() have no
     return value.

FILES
     /etc/group  group database file

COMPATIBILITY
     The historic function setgrfile(), which allowed the specification of
     alternate group databases, has been deprecated and is no longer avail-
     able.

SEE ALSO
     getpwent(3), group(5), mbr_gid_to_uuid(3,) opendirectory(8), yp(8)

STANDARDS
     The getgrent(), getgrnam(), getgrnam_r(), getgrgid(), getgrgid_r() and
     endgrent() functions conform to ISO/IEC 9945-1:1996 (``POSIX.1'').  The
     setgrent() function differs from that standard in that its return type is
     int rather than void.

HISTORY
     The functions endgrent(), getgrent(), getgrnam(), getgrgid(), and
     setgrent() appeared in Version 7 AT&T UNIX.  The functions setgrfile()
     and setgroupent() appeared in 4.3BSD-Reno.  The functions getgrnam_r()
     and getgrgid_r() appeared in FreeBSD 5.1.  The functions getgruuid() and
     getgruuid_r() appeared in Mac OS X 10.8.

BUGS
     The functions getgrent(), getgrnam(), getgrgid(), getgruuid(),
     setgroupent() and setgrent() leave their results in an internal thread-
     specific memory and return a pointer to that object.  Subsequent calls to
     the same function will modify the same object.

BSD                            October 26, 2011                            BSD