.\" Copyright (c) 1989, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" From: @(#)getgrent.3 8.2 (Berkeley) 4/19/94 .\" $FreeBSD: src/lib/libc/gen/getgrent.3,v 1.16 2001/10/01 16:08:51 ru Exp $ .\" .Dd September 29, 1994 .Dt GETGRENT 3 .Os .Sh NAME .Nm endgrent , .Nm getgrent , .Nm getgrgid , .Nm getgrgid_r , .Nm getgrnam , .Nm getgrnam_r , .Nm setgrent , .\" .Nm setgrfile , .Nm setgroupent .Nd group database operations .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In grp.h .Ft void .Fo endgrent .Fa void .Fc .Ft struct group * .Fo getgrent .Fa void .Fc .Ft struct group * .Fo getgrgid .Fa "gid_t gid" .Fc .Ft int .Fo getgrgid_r .Fa "gid_t gid" .Fa "struct group *grp" .Fa "char *buffer" .Fa "size_t bufsize" .Fa "struct group **result" .Fc .Ft struct group * .Fo getgrnam .Fa "const char *name" .Fc .Ft int .Fo getgrnam_r .Fa "const char *name" .Fa "struct group *grp" .Fa "char *buffer" .Fa "size_t bufsize" .Fa "struct group **result" .Fc .Ft void .Fo setgrent .Fa void .Fc .\" .Ft void .\" .Fn setgrfile "const char *name" .Ft int .Fo setgroupent .Fa "int stayopen" .Fc .Sh DESCRIPTION These functions operate on the group database file .Pa /etc/group , which is described in .Xr group 5 . Each line of the database is defined by the structure .Ar group , found in the include file .Aq Pa grp.h : .Bd -literal -offset indent struct group { char *gr_name; /* group name */ char *gr_passwd; /* group password */ int gr_gid; /* group id */ char **gr_mem; /* group members */ }; .Ed .Pp The functions .Fn getgrnam and .Fn getgrgid search the group database for the given group name (pointed to by .Ar name ) or the group id (pointed to by .Ar gid ) , respectively, returning the first one encountered. Identical group names or group ids may result in undefined behavior. .Pp All of these routines are thread-safe. The .Fn getgrent , .Fn getgrgid , and .Fn getgrnam routines return a pointer to a result managed by the system library in a thread-specific data structure. Every thread has space for a pointer to a struct group and allocates its own storage for the result. Neither previously returned values in memory nor a previously returned pointer value should be used by a thread after calling any one of these three routines. Memory allocated by a thread is automatically released on subsequent calls by the same thread to any of these three routines, and when the thread exits. .Pp The functions .Fn getgrgid_r and .Fn getgrnam_r take additional arguments which supply storage space for the returned result. The .Fa grp parameter is a pointer to a struct group, which must be allocated by the caller. The .Fa buffer parameter is a pointer to a block of memory with a size specified by .Pa bufsize . This buffer is used to hold the values which are pointed to by values filled in the .Fa grp structure. Zero is returned on success. If insufficient memory is supplied, these routines return ERANGE. .Pp The .Fn getgrent function sequentially reads the group database and is intended for programs that wish to step through the complete list of groups. .Pp All three routines will open the group file for reading, if necessary. .Pp The .Fn setgroupent function opens the file, or rewinds it if it is already open. If .Fa stayopen is non-zero, file descriptors are left open, significantly speeding functions' subsequent calls. This functionality is unnecessary for .Fn getgrent , as it doesn't 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. .Pp The .Fn setgrent function is identical to .Fn setgroupent with an argument of zero. .Pp The .Fn endgrent function closes any open files. .Sh RETURN VALUES The functions .Fn getgrent , .Fn getgrgid , and .Fn getgrnam each 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 function .Fn setgroupent returns the value 1 if successful; otherwise, the value 0 is returned. The functions .Fn endgrent , .Fn setgrent , and .Fn setgrfile have no return value. .Sh FILES .Bl -tag -width /etc/group -compact .It Pa /etc/group group database file .El .Sh LEGACY SYNOPSIS .Fd #include .Pp .Ft int .br .Fo setgrent .Fa void .Fc ; .Pp The function .Fn setgrent returns the value 1 if successful; otherwise, the value 0 is returned. .Sh SEE ALSO .Xr getpwent 3 , .Xr yp 8 , .Xr group 5 .Sh HISTORY The functions .Fn endgrent , .Fn getgrent , .Fn getgrnam , .Fn getgrgid , and .Fn setgrent appeared in .At v7 . The functions .Fn setgrfile and .Fn setgroupent appeared in .Bx 4.3 Reno . .Sh COMPATIBILITY The historic function .Fn setgrfile , which allowed the specification of alternate password databases, has been deprecated and is no longer available. .Sh BUGS The functions .Fn getgrent , .Fn getgrnam , and .Fn getgrgid , leave their results in internal thread-specific memory and return a pointer to that object. Subsequent calls to any of these three routines by the same thread will release the object and return a new pointer value.