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.\"     @(#)devname.3	8.2 (Berkeley) 4/29/95
.\" $FreeBSD: src/lib/libc/gen/devname.3,v 1.7.2.7 2003/03/15 15:11:05 trhodes Exp $
.\" $DragonFly: src/lib/libc/gen/devname.3,v 1.5 2007/05/17 08:19:00 swildner Exp $
.\"
.Dd August 11, 2009
.Dt DEVNAME 3
.Os
.Sh NAME
.Nm devname ,
.Nm devname_r ,
.Nm fdevname ,
.Nm fdevname_r
.Nd get device name
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/stat.h
.In stdlib.h
.Ft char *
.Fn devname "dev_t dev" "mode_t type"
.Ft char *
.Fn devname_r "dev_t dev" "mode_t type" "char *buf" "size_t len"
.Ft char *
.Fn fdevname "int fd"
.Ft int
.Fn fdevname_r "int fd" "char *buf" "size_t len"
.Sh DESCRIPTION
The
.Fn devname
and
.Fn devname_r
functions return a pointer to the name of the block or character
device in
.Pa /dev
with a device number of
.Fa dev ,
and a file type matching the one encoded in
.Fa type
which must be one of
.Dv S_IFBLK
or
.Dv S_IFCHR .
To find the right name,
.Fn devname
and
.Fn devname_r
first search the device database created by
.Xr dev_mkdb 8 ;
if that fails, it will format the information encapsulated in
.Fa dev
and
.Fa type
in a human-readable format.
.Pp
The
.Fn fdevname
and
.Fn fdevname_r
function obtain the device name directly from a file descriptor
pointing to a character device.
.Pp
.Fn devname
and
.Fn fdevname
returns a pointer to an internal static object; thus, subsequent calls will
modify the same buffer.
.Fn devname_r
and
.Fn fdevname_r
avoid this problem by taking a buffer
.Fa buf
and a buffer length
.Fa len
as arguments.
.Sh RETURN VALUES
The
.Fn devname ,
.Fn devname_r
and
.Fn fdevname
functions return a pointer to the name of the block or character
device in
.Pa /dev
if successful; otherwise
.Dv NULL
is returned.
If
.Fn fdevname
fails,
.Va errno
is set to indicate the error.
.Pp
The
.Fn fdevname_r
function returns 0 if successful.
Otherwise an error number is returned.
.Sh ERRORS
The
.Fn fdevname
and
.Fn fdevname_r
functions may fail and return the following error codes:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
is not a valid open file descriptor.
.It Bq Er EINVAL
The
.Fa fd
must belong to a character device.
.El
.Pp
The
.Fn fdevname_r
function may fail and return the following error code:
.Bl -tag -width Er
.It Bq Er ERANGE
The
.Fa len
argument is smaller than the length of the string to be returned.
.El
.Sh SEE ALSO
.Xr stat 2 ,
.Xr dev_mkdb 8
.Sh HISTORY
The
.Fn devname
function appeared in
.Bx 4.4 .
.Pp
The
.Fn devname_r
function appeared in
.Dx 1.0
and the
.Fn fdevname
and
.Fn fdevname_r
functions appeared in
.Dx 2.3 .