.\" $OpenBSD: getgrent.3,v 1.16 2008/07/28 20:19:32 jmc Exp $ .\" .\" 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. 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. .\" .Dd $Mdocdate: July 28 2008 $ .Dt GETGRENT 3 .Os .Sh NAME .Nm getgrent , .Nm getgrnam , .Nm getgrnam_r , .Nm getgrgid , .Nm getgrgid_r , .Nm setgroupent , .\" .Nm setgrfile , .Nm setgrent , .Nm endgrent .Nd group database operations .Sh SYNOPSIS .Fd #include .Fd #include .Ft struct group * .Fn getgrent void .Ft struct group * .Fn getgrnam "const char *name" .Ft int .Fn getgrnam_r "const char *name" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result" .Ft struct group * .Fn getgrgid "gid_t gid" .Ft int .Fn getgrgid_r "gid_t gid" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result" .Ft int .Fn setgroupent "int stayopen" .\" .Ft void .\" .Fn setgrfile "const char *name" .Ft void .Fn setgrent void .Ft void .Fn endgrent void .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 .Li struct 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 */ gid_t 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 .Fa name or the group ID pointed to by .Fa gid , respectively, returning the first one encountered. Identical group names or group GIDs may result in undefined behavior. .Pp .Fn getgrent 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 .Fn setgroupent opens the file, or rewinds it if it is already open. If .Fa stayopen is non-zero, file descriptors are left open, significantly speeding subsequent function 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 .Fn setgrent is equivalent to .Fn setgroupent with an argument of zero. .Pp The .Fn endgrent function closes any open files. .Pp The .Fn getgrgid_r and .Fn getgrnam_r functions both update the group structure pointed to by .Fa grp and store a pointer to that structure at the location pointed to by .Fa result . The structure is filled with an entry from the group database with a matching .Fa gid or .Fa name . Storage referenced by the group structure will be allocated from the memory provided with the .Fa buffer parameter, which is .Fa bufsiz characters in size. .\" The maximum size needed for this buffer can be determined with the .\" .Dv _SC_GETGR_R_SIZE_MAX .\" .Xr sysconf 2 .\" parameter. .Sh YP SUPPORT If YP is active, the functions .Fn getgrent and .Fn getgrnam also use the .Pa group.byname YP map and the function .Fn getgrgid also uses the .Pa group.bygid YP map in addition to the group file, respecting the order of normal and YP entries in the group file. .Sh RETURN VALUES The functions .Fn getgrent , .Fn getgrnam , and .Fn 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 .Fn setgroupent function returns the value 1 if successful, otherwise 0. The .Fn endgrent and .Fn setgrent functions have no return value. The functions .Fn getgrgid_r and .Fn getgrnam_r store a null pointer at the location pointed to by .Fa result and return the error number if an error occurs, or the requested entry is not found. .Sh FILES .Bl -tag -width /etc/group -compact .It Pa /etc/group group database file .El .Sh SEE ALSO .Xr getpwent 3 , .Xr ypclnt 3 , .Xr group 5 , .Xr yp 8 .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 . .Pp The historic function .Xr setgrfile 3 , which allowed the specification of alternate group databases, has been deprecated and is no longer available. .Sh BUGS The functions .Fn getgrent , .Fn getgrnam , .Fn getgrgid , .Fn setgroupent , and .Fn 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. .Pp The functions .Fn getgrent , .Fn endgrent , .Fn setgroupent , and .Fn setgrent are fairly useless in a networked environment and should be avoided, if possible.