xref: /freebsd/lib/libc/gen/devname.3 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)

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.Dd February 22, 2005
.Dt DEVNAME 3
.Os
.Sh NAME
.Nm devname
.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" "int len"
.Ft char *
.Fn fdevname "int fd"
.Ft char *
.Fn fdevname_r "int fd" "char *buf" "int len"
.Sh DESCRIPTION
The
.Fn devname
function returns 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
asks the kernel via the
.Va kern.devname
sysctl.
If it is unable to come up with a suitable name,
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 obtains the device name directly from a file descriptor
pointing to a character device.
If it is unable to come up with a suitable name, these functions will
return a NULL pointer.
.Pp
.Fn devname
and
.Fn fdevname
return the name stored in a static buffer which will be overwritten
on subsequent calls.
.Fn devname_r
and
.Fn fdevname_r
take a buffer and length as argument to avoid this problem.
.Sh EXAMPLES
.Bd -literal -compact
int fd;
struct stat buf;
char *name;

	fd = open("/dev/tun");
	fstat(fd, &buf);
	printf("devname is /dev/%s\en", devname(buf.st_rdev, S_IFCHR));
	printf("fdevname is /dev/%s\en", fdevname(fd));
.Ed
.Sh SEE ALSO
.Xr stat 2
.Sh HISTORY
The
.Fn devname
function appeared in
.Bx 4.4 .
The
.Fn fdevname
function appeared in
.Fx 8.0 .