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.\" $OpenBSD: user_from_uid.3,v 1.1 2019/09/02 21:18:41 deraadt 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
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.\" 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.
.\"
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.\" 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)
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd $Mdocdate: September 2 2019 $
.Dt USER_FROM_UID 3
.Os
.Sh NAME
.Nm user_from_uid ,
.Nm uid_from_user ,
.Nm group_from_gid ,
.Nm gid_from_group
.Nd cache password and group entries
.Sh SYNOPSIS
.In pwd.h
.Ft int
.Fn uid_from_user "const char *name" "uid_t *uid"
.Ft const char *
.Fn user_from_uid "uid_t uid" "int nouser"
.In grp.h
.Ft int
.Fn gid_from_group "const char *name" "gid_t *gid"
.Ft const char *
.Fn group_from_gid "gid_t gid" "int nogroup"
.Sh DESCRIPTION
The
.Fn user_from_uid
function returns the user name associated with the argument
.Fa uid .
The user name is cached so that multiple calls with the same
.Fa uid
do not require additional calls to
.Xr getpwuid 3 .
If there is no user associated with the
.Fa uid ,
a pointer is returned
to a string representation of the
.Fa uid ,
unless the argument
.Fa nouser
is non-zero, in which case a null pointer is returned.
.Pp
The
.Fn uid_from_user
function returns the user ID associated with the argument
.Fa name .
The user ID is cached so that multiple calls with the same
.Fa name
do not require additional calls to
.Xr getpwnam 3 .
If there is no user ID associated with the
.Fa name ,
the
.Fn uid_from_user
function returns -1;
otherwise it stores the user ID at the location pointed to by
.Fa uid
and returns 0.
.Pp
The
.Fn group_from_gid
function returns the group name associated with the argument
.Fa gid .
The group name is cached so that multiple calls with the same
.Fa gid
do not require additional calls to
.Xr getgrgid 3 .
If there is no group associated with the
.Fa gid ,
a pointer is returned
to a string representation of the
.Fa gid ,
unless the argument
.Fa nogroup
is non-zero, in which case a null pointer is returned.
.Pp
The
.Fn gid_from_group
function returns the group ID associated with the argument
.Fa name .
The group ID is cached so that multiple calls with the same
.Fa name
do not require additional calls to
.Xr getgrnam 3 .
If there is no group ID associated with the
.Fa name ,
the
.Fn gid_from_group
function returns -1;
otherwise it stores the group ID at the location pointed to by
.Fa gid
and returns 0.
.Sh SEE ALSO
.Xr getgrgid 3 ,
.Xr getpwuid 3
.Sh HISTORY
The
.Fn user_from_uid
and
.Fn group_from_gid
functions first appeared in
.Bx 4.4 .
.Pp
The
.Fn uid_from_user
and
.Fn gid_from_group
functions were ported from
.Nx
and first appeared in
.Ox 6.4 .
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