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288 lines
6.7 KiB
Groff
288 lines
6.7 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" From: @(#)getgrent.3 8.2 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd April 16, 2003
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.Dt GETGRENT 3
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.Os
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.Sh NAME
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.Nm getgrent ,
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.Nm getgrent_r ,
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.Nm getgrnam ,
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.Nm getgrnam_r ,
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.Nm getgrgid ,
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.Nm getgrgid_r ,
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.Nm setgroupent ,
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.Nm setgrent ,
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.Nm endgrent
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.Nd group database operations
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In grp.h
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.Ft struct group *
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.Fn getgrent void
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.Ft int
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.Fn getgrent_r "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result"
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.Ft struct group *
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.Fn getgrnam "const char *name"
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.Ft int
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.Fn getgrnam_r "const char *name" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result"
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.Ft struct group *
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.Fn getgrgid "gid_t gid"
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.Ft int
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.Fn getgrgid_r "gid_t gid" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result"
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.Ft int
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.Fn setgroupent "int stayopen"
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.Ft int
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.Fn setgrent void
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.Ft void
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.Fn endgrent void
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.Sh DESCRIPTION
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These functions operate on the group database file
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.Pa /etc/group
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which is described
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in
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.Xr group 5 .
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Each line of the database is defined by the structure
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.Vt group
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found in the include
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file
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.In grp.h :
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.Bd -literal -offset indent
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struct group {
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char *gr_name; /* group name */
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char *gr_passwd; /* group password */
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gid_t gr_gid; /* group id */
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char **gr_mem; /* group members */
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};
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.Ed
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.Pp
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The functions
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.Fn getgrnam
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and
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.Fn getgrgid
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search the group database for the given group name pointed to by
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.Fa name
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or the group id pointed to by
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.Fa gid ,
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respectively, returning the first one encountered.
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Identical group
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names or group gids may result in undefined behavior.
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.Pp
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The
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.Fn getgrent
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function
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sequentially reads the group database and is intended for programs
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that wish to step through the complete list of groups.
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.Pp
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The functions
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.Fn getgrent_r ,
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.Fn getgrnam_r ,
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and
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.Fn getgrgid_r
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are thread-safe versions of
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.Fn getgrent ,
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.Fn getgrnam ,
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and
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.Fn getgrgid ,
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respectively.
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The caller must provide storage for the results of the search in
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the
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.Fa grp ,
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.Fa buffer ,
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.Fa bufsize ,
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and
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.Fa result
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arguments.
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When these functions are successful, the
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.Fa grp
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argument will be filled-in, and a pointer to that argument will be
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stored in
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.Fa result .
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If an entry is not found or an error occurs,
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.Fa result
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will be set to
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.Dv NULL .
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.Pp
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These functions will open the group file for reading, if necessary.
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.Pp
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The
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.Fn setgroupent
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function
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opens the file, or rewinds it if it is already open.
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If
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.Fa stayopen
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is non-zero, file descriptors are left open, significantly speeding
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functions subsequent calls.
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This functionality is unnecessary for
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.Fn getgrent
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as it does not close its file descriptors by default.
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It should also
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be noted that it is dangerous for long-running programs to use this
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functionality as the group file may be updated.
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.Pp
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The
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.Fn setgrent
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function
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is identical to
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.Fn setgroupent
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with an argument of zero.
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.Pp
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The
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.Fn endgrent
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function
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closes any open files.
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.Sh RETURN VALUES
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The functions
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.Fn getgrent ,
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.Fn getgrnam ,
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and
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.Fn getgrgid ,
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return a pointer to a group structure on success or
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.Dv NULL
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if the entry is not found or if an error occurs.
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If an error does occur,
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.Va errno
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will be set.
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Note that programs must explicitly set
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.Va errno
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to zero before calling any of these functions if they need to
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distinguish between a non-existent entry and an error.
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The functions
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.Fn getgrent_r ,
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.Fn getgrnam_r ,
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and
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.Fn getgrgid_r
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return 0 if no error occurred, or an error number to indicate failure.
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It is not an error if a matching entry is not found.
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(Thus, if
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.Fa result
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is set to
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.Dv NULL
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and the return value is 0, no matching entry exists.)
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.Pp
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The functions
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.Fn setgroupent
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and
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.Fn setgrent
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return the value 1 if successful, otherwise the value
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0 is returned.
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The functions
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.Fn endgrent
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and
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.Fn setgrfile
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have no return value.
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.Sh FILES
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.Bl -tag -width /etc/group -compact
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.It Pa /etc/group
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group database file
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.El
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.Sh COMPATIBILITY
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The historic function
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.Fn setgrfile ,
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which allowed the specification of alternate password databases, has
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been deprecated and is no longer available.
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.Sh SEE ALSO
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.Xr getpwent 3 ,
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.Xr group 5 ,
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.Xr nsswitch.conf 5 ,
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.Xr yp 8
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.Sh STANDARDS
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The
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.Fn getgrent ,
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.Fn getgrnam ,
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.Fn getgrnam_r ,
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.Fn getgrgid ,
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.Fn getgrgid_r
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and
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.Fn endgrent
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functions conform to
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.St -p1003.1-96 .
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The
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.Fn setgrent
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function differs from that standard in that its return type is
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.Vt int
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rather than
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.Vt void .
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.Sh HISTORY
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The functions
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.Fn endgrent ,
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.Fn getgrent ,
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.Fn getgrnam ,
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.Fn getgrgid ,
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and
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.Fn setgrent
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appeared in
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.At v7 .
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The functions
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.Fn setgrfile
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and
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.Fn setgroupent
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appeared in
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.Bx 4.3 Reno .
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The functions
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.Fn getgrent_r ,
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.Fn getgrnam_r ,
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and
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.Fn getgrgid_r
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appeared in
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.Fx 5.1 .
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.Sh BUGS
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The functions
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.Fn getgrent ,
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.Fn getgrnam ,
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.Fn getgrgid ,
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.Fn setgroupent
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and
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.Fn setgrent
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leave their results in an internal static object and return
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a pointer to that object.
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Subsequent calls to
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the same function
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will modify the same object.
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.Pp
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The functions
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.Fn getgrent ,
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.Fn getgrent_r ,
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.Fn endgrent ,
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.Fn setgroupent ,
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and
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.Fn setgrent
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are fairly useless in a networked environment and should be
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avoided, if possible.
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The
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.Fn getgrent
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and
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.Fn getgrent_r
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functions
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make no attempt to suppress duplicate information if multiple
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sources are specified in
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.Xr nsswitch.conf 5 .
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