Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help 
GETGRENT(3)		     Library Functions Manual		     GETGRENT(3)

NAME
     getgrent,	 getgrent_r,   getgrnam,   getgrnam_r,	 getgrgid,   getgrgid_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 bufsize,
	 struct group **result);

     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
     setgroupent(int stayopen);

     void
     setgrent(void);

     void
     endgrent(void);

DESCRIPTION
     These functions operate on the group database file /etc/group which is  de-
     scribed 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,  re-
     spectively,  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.

     The  functions getgrent_r(), getgrnam_r(), and getgrgid_r() are thread-safe
     versions of getgrent(),  getgrnam(),  and	getgrgid(),  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 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 unneces-
     sary  for	getgrent() as it does not close its file descriptors by default.
     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.

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	programs
     must  explicitly set errno to zero before calling any of these functions if
     they need to distinguish between a non-existent entry and	an  error.   The
     functions getgrent_r(), getgrnam_r(), and getgrgid_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  re-
     turn value is 0, no matching entry exists.)

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

FILES
     /etc/group  group database file

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

SEE ALSO
     getpwent(3), group(5), nsswitch.conf(5), yp(8)

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

HISTORY
     The  functions  endgrent(),  getgrent(),  getgrnam(),  getgrgid(), and set-
     grent() appeared in Version 7 AT&T UNIX.	The  functions	setgrfile()  and
     setgroupent()  appeared in 4.3BSD-Reno.  The functions getgrent_r(), getgr-
     nam_r(), and getgrgid_r() appeared in FreeBSD 5.1.

BUGS
     The functions getgrent(), getgrnam(), getgrgid(),	setgroupent()  and  set-
     grent()  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(), getgrent_r(), endgrent(), setgroupent(), and set-
     grent()  are  fairly  useless  in	a  networked  environment  and should be
     avoided, if possible.  The getgrent() and getgrent_r()  functions	make  no
     attempt to suppress duplicate information if multiple sources are specified
     in nsswitch.conf(5).

FreeBSD ports 15.1		  July 31, 2016 		     GETGRENT(3)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=getgrent&manpath=FreeBSD+15.1-RELEASE+and+Ports>

home | help