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

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

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <grp.h>

     struct group *
     getgrent(void);

     int
     getgrent_r(struct group *grp, char	*buffer, size_t	buflen,
	 struct	group **result);

     struct group *
     getgrgid(gid_t gid);

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

     struct group *
     getgrnam(const char *name);

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

     int
     setgroupent(int stayopen);

     void
     setgrent(void);

     void
     endgrent(void);

DESCRIPTION
     These functions operate on	the group database 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 ids 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 functions will open the group file for reading, if necessary.

     The functions getgrnam_r(), getgrgid_r(), and getgrent_r()	act like their
     non re-entrant counterparts respectively, updating	the contents of	grp
     and storing a pointer to that in result, and returning 0.	Storage	used
     by	grp is allocated from buffer, which is buflen bytes in size.  If the
     requested entry cannot be found, result will point	to NULL	and 0 will be
     returned.	If an error occurs, a non-zero error number will be returned
     and result	will point to NULL.  Calling getgrent_r() from multiple
     threads will result in each thread	reading	a disjoint portion of the
     group database.

     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	equivalent to setgroupent() with an argument
     of	zero.

     The endgrent() function closes any	open files.

RETURN VALUES
     The functions getgrgid(), getgrnam(), and getgrent() return a valid
     pointer to	a group	structure on success and a NULL	pointer	if the entry
     was not found or an error occured.	 If an error occured, the global vari-
     able errno	is set to indicate the nature of the failure.

     The functions getgrgid_r(), getgrnam_r(), and getgrent_r()	return 0 on
     success or	entry not found, and non-zero on failure, setting the global
     variable errno to indicate	the nature of the failure.

     The setgroupent() function	returns	the value 1 if successful, otherwise
     the value 0 is returned, setting the global variable errno	to indicate
     the nature	of the failure.

     The endgrent() and	setgrent() functions have no return value.

FILES
     /etc/group	 group database	file

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

ERRORS
     The following error codes may be set in errno for getgrent, getgrent_r,
     getgrnam, getgrnam_r, getgrgid, getgrgid_r, and setgroupent:

     [EINTR]		A signal was caught during the database	search.

     [EIO]		An I/O error has occurred.

     [EMFILE]		The limit on open files	for this process has been
			reached.

     [ENFILE]		The system limit on open files has been	reached.

     The following error code may be set in errno for getgrent_r, getgrnam_r,
     and getgrgid_r:

     [ERANGE]		The resulting struct group does	not fit	in the space
			defined	by buffer and buflen

     Other errno values	may be set depending on	the specific database back-
     ends.

SEE ALSO
     getpwent(3), group(5), nsswitch.conf(5)

STANDARDS
     The getgrgid() and	getgrnam() functions conform to	ISO/IEC	9945-1:1990
     ("POSIX.1").  The getgrgid_r() and	getgrnam_r() functions conform to IEEE
     Std 1003.1c-1995 ("POSIX.1").  The	endgrent(), getgrent(),	and setgrent()
     functions conform to X/Open Portability Guide Issue 4, Version 2
     ("XPG4.2")	and IEEE Std 1003.1-2004 ("POSIX.1") (XSI extension).

HISTORY
     The functions endgrent(), getgrent(), getgrgid(), getgrnam(), and
     setgrent()	appeared in Version 7 AT&T UNIX.  The functions	setgrfile()
     and setgroupent() appeared	in 4.3BSD-Reno.	 The functions getgrgid_r()
     and getgrnam_r() appeared in NetBSD 3.0.

BUGS
     The functions getgrent(), getgrgid(), getgrnam(), 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 mod-
     ify the same object.

     The functions getgrent(), endgrent(), setgroupent(), and setgrent() are
     fairly useless in a networked environment and should be avoided, if pos-
     sible.  getgrent()	makes no attempt to suppress duplicate information if
     multiple sources are specified in nsswitch.conf(5)

BSD				April 30, 2008				   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | FILES | COMPATIBILITY | ERRORS | SEE ALSO | STANDARDS | HISTORY | BUGS

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