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

NAME
     getgrent, getgrnam, getgrgid, setgroupent, setgrent, endgrent,
     getgrent_r, getgrnam_r, getgrgid_r, setgrent_r, endgrent_r - group
     database operations

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

     struct group *
     getgrent(void);

     struct group *
     getgrnam(const char *name);

     struct group *
     getgrgid(gid_t gid);

     int
     setgroupent(int stayopen);

     int
     setgrent(void);

     void
     endgrent(void);

     struct group *
     getgrent_r(struct group *space, char *buf, int buflen);

     int
     getgrnam_r(const char *name, struct group *space, char *buf,
	     size_t bufsize, struct group **result);

     int
     getgrgid_r(gid_t gid, struct group *space, char *buf, size_t bufsize,
	     struct group **result);

     void
     setgrent_r(void);

     void
     endgrent_r(void);

DESCRIPTION
     These functions operate on the group database file /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() and getgrgid() search the group database for the
     given group name pointed to by name or the group id pointed to by gid,
     respectively, returning the first one encountered.	 Identical group names
     or group gids may result in undefined behavior.

     The getgrent() function sequentially reads the group database and is in-
     tended for programs that wish to step through the complete list of
     groups.

     All three routines will open the group file for reading, if necessary.

     The setgroupent() function opens the file, or rewinds it if it is already
     open.  If stayopen is non-zero, file descriptors are left open, signifi-
     cantly speeding functions subsequent calls.  This functionality is unnec-
     essary for getgrent() as it doesn't close its file descriptors by de-
     fault.  It should also be noted that it is dangerous for long-running
     programs to use this functionality as the group file may be updated.

     The setgrent() function is identical to setgroupent() with an argument of
     zero.

     The endgrent() function closes any open files.

     The ``r-suffixed'' functions getgrent_r(), getgrnam_r(), getgrgid_r(),
     setgrent_r(), and endgrent_r() functions are reentrant versions of their
     corresponding non-reentrant functions.  Those that build a group struc-
     ture must be provided a pointer space to a structure that will hold the
     result, as well as a buffer and its size (buflen or bufsize) for memory
     to which members of space may be pointed.	The built-up structure will
     either be returned directly (getgrent_r()), or stored via the result pa-
     rameter.  This will be NULL if the given group name or ID does not exist.
     For example:

	   struct group space, *gp;
	   int error;
	   char buf[SIZE]; /* where SIZE >= sysconf(_SC_GETGR_R_SIZE_MAX) */
	   error = getgrnam_r(groupname, &space, buf, sizeof buf, &gp);
	   if (gp != NULL) {
	       /* group exists; gp == &space */
	       printf("group %s, gid %ld\n", gp->gr_name, (long)gp->gr_uid);
	   } else
	       ... group does not exist, or an error occurred ...

RETURN VALUES
     The functions getgrent(), getgrent_r(), getgrnam(), and getgrgid() return
     a pointer to the group entry if successful; if end-of-file is reached or
     an error occurs a null pointer is returned.  The functions getgrnam_r()
     and getgrgid_r() return 0 on success, or an error number on failure.  The
     functions setgroupent() and setgrent() return the value 1 if successful,
     otherwise the value 0 is returned.	 The functions endgrent(),
     setgrent_r(), and endgrent_r() have no return value.

     If the buffer supplied to the reentrant functions is too small, they will
     fail with an ERANGE error.	 The POSIX functions getgrnam_r() and
     getgruid_r() will return ERANGE, while getgrent_r() will set the global
     variable errno instead.

FILES
     /etc/group	 group database file

SEE ALSO
     getpwent(3), group(5)

HISTORY
     The functions endgrent(), getgrent(), getgrnam(), getgrgid(), and
     setgrent() appeared in Version 7 AT&T UNIX.  The function setgroupent()
     appeared in 4.3BSD-Reno.

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

     The functions getgrent(), endgrent(), setgroupent(), and setgrent() are
     fairly useless in a networked environment and should be avoided, if pos-
     sible.

     The getgrent(), endgrent(), setgroupent(), and setgrent() functions may
     not be safely called concurrently from multiple threads, e.g., the inter-
     faces described by pthreads(3).

     The non-standard functions setgrent(), setgrent_r(), getgrent_r(), and
     endgrent_r() are known to have different interfaces on different systems,
     and should probably be avoided.

     The ``interesting'' calling sequences for the reentrant functions are
     courtesy of ongoing standardization efforts.

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

     The getgrnam(), getgrgid(), getgrnam_r(), and getgrgid_r() functions con-
     form to IEEE Std1003.1-1996 (``POSIX'').

BSDI BSD/OS			April 27, 2001				     3
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