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.\"     @(#)pwcache.3	8.1 (Berkeley) 6/9/93
.\"
.Dd May 5, 2020
.Dt PWCACHE 3
.Os
.Sh NAME
.Nm pwcache ,
.Nm user_from_uid ,
.Nm group_from_gid
.Nd cache password and group entries
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In pwd.h
.Ft const char *
.Fn user_from_uid "uid_t uid" "int nouser"
.Ft int
.Fn uid_from_user "const char *name" "uid_t *uid"
.Ft int
.Fn pwcache_userdb "int (*setpassent)(int)" "void (*endpwent)(void)" "struct passwd * (*getpwnam)(const char *)" "struct passwd * (*getpwuid)(uid_t)"
.In grp.h
.Ft const char *
.Fn group_from_gid "gid_t gid" "int nogroup"
.Ft int
.Fn gid_from_group "const char *name" "gid_t *gid"
.Ft int
.Fn pwcache_groupdb "int (*setgroupent)(int)" "void (*endgrent)(void)" "struct group * (*getgrnam)(const char *)" "struct group * (*getgrgid)(gid_t)"
.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
.Dv NULL
pointer is returned.
.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
.Dv NULL
pointer is returned.
.Pp
The
.Fn uid_from_user
function returns the uid associated with the argument
.Fa name .
The uid is cached so that multiple calls with the same
.Fa name
do not require additional calls to
.Xr getpwnam 3 .
If there is no uid associated with the
.Fa name ,
the
.Fn uid_from_user
function returns \-1; otherwise it stores the uid at the location pointed to by
.Fa uid
and returns 0.
.Pp
The
.Fn gid_from_group
function returns the gid associated with the argument
.Fa name .
The gid is cached so that multiple calls with the same
.Fa name
do not require additional calls to
.Xr getgrnam 3 .
If there is no gid associated with the
.Fa name ,
the
.Fn gid_from_group
function returns \-1; otherwise it stores the gid at the location pointed to by
.Fa gid
and returns 0.
.Pp
The
.Fn pwcache_userdb
function changes the user database access routines which
.Fn user_from_uid
and
.Fn uid_from_user
call to search for users.
The caches are flushed and the existing
.Fn endpwent
method is called before switching to the new routines.
.Fa getpwnam
and
.Fa getpwuid
must be provided, and
.Fa setpassent
and
.Fa endpwent
may be
.Dv NULL
pointers.
.Pp
The
.Fn pwcache_groupdb
function changes the group database access routines which
.Fn group_from_gid
and
.Fn gid_from_group
call to search for groups.
The caches are flushed and the existing
.Fn endgrent
method is called before switching to the new routines.
.Fa getgrnam
and
.Fa getgrgid
must be provided, and
.Fa setgroupent
and
.Fa endgrent
may be
.Dv NULL
pointers.
.Sh ERRORS
If insufficient memory is available,
.Fn user_from_uid
and
.Fn group_from_gid
may return NULL pointers.
.Va errno
is set to
.Er ENOMEM .
.Sh SEE ALSO
.Xr getgrgid 3 ,
.Xr getgrnam 3 ,
.Xr getpwnam 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 first appeared in
.Nx 1.4 .
.Pp
The
.Fn pwcache_userdb
and
.Fn pwcache_groupdb
functions first appeared in
.Nx 1.6
and
.Fx 10.0 .