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.\"     @(#)devname.3	8.2 (Berkeley) 4/29/95
.\"
.Dd September 9, 2017
.Dt DEVNAME 3
.Os
.Sh NAME
.Nm devname ,
.Nm devname_r
.Nd get device name
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.In sys/stat.h
.Ft char *
.Fn devname "dev_t dev" "mode_t type"
.Ft int
.Fn devname_r "dev_t dev" "mode_t type" "char *path" "size_t len"
.Sh DESCRIPTION
The
.Fn devname
function returns a pointer to the static buffer with the name of the
block or character device in
.Dq 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 S_IFBLK or S_IFCHR.
If no device matches the specified values, or no information is
available,
.Dv NULL
is returned.
.Pp
The
.Fn devname_r
function is a reentrant and thread-safe version of
.Fn devname .
This function returns the device name by copying it into the
.Fa path
argument with up to
.Fa len
characters.
The
.Fa path
argument is always nul-terminated.
.Pp
The traditional display for applications when no device is
found is the string
.Dq ?? .
.Sh RETURN VALUES
If successful,
.Fn devname
returns a pointer to a nul-terminated string containing the name of the device.
If an error occurs
.Fa devname
will return
.Dv NULL .
.Pp
If successful,
.Fn devname_r
places a nul-terminated string containing the name of the device in
the buffer pointed to by
.Ar path
and returns 0.
If an error occurs
.Fn devname_r
will return an error number from
.In sys/errno.h
indicating what went wrong.
.Sh FILES
.Bl -tag -width /var/run/dev.cdb -compact
.It Pa /var/run/dev.cdb
Device database file.
.El
.Sh ERRORS
The
.Fn devname_r
function may fail if:
.Bl -tag -width Er
.It Bq Er ENOENT
The corresponding device does not exist.
.It Bq Er ERANGE
The passed buffer length is too short.
.El
.Sh SEE ALSO
.Xr stat 2 ,
.Xr dev_mkdb 8
.Sh HISTORY
The
.Nm devname
function call appeared in
.Bx 4.4 .
.Pp
The
.Fn devname_r
function first appeared in
.Nx 6.0 .