NAME
devname,
devname_r, fdevname,
fdevname_r —
get device name
LIBRARY
library “libc”
SYNOPSIS
#include
<sys/stat.h>
#include <stdlib.h>
char *
devname(dev_t
dev, mode_t
type);
char *
devname_r(dev_t
dev, mode_t type,
char *buf,
size_t len);
char *
fdevname(int
fd);
int
fdevname_r(int
fd, char *buf,
size_t len);
DESCRIPTION
Thedevname()
and
devname_r()
functions return a pointer to the name of the block or character device in
/dev with a device number of
dev, and a file type matching the one encoded in
type which must be one of
S_IFBLK or S_IFCHR. To find
the right name, devname() and
devname_r() asks the kernel via the
kern.devname sysctl. If it fails, it will format the
information encapsulated in dev and
type in a human-readable format.
The
fdevname()
and
fdevname_r()
function obtain the device name directly from a file descriptor pointing to
a character device.
devname()
and fdevname() returns a pointer to an internal
static object; thus, subsequent calls will modify the same buffer.
devname_r() and fdevname_r()
avoid this problem by taking a buffer buf and a buffer
length len as arguments.
RETURN VALUES
The devname(),
devname_r() and fdevname()
functions return a pointer to the name of the block or character device in
/dev if successful; otherwise
NULL is returned. If
fdevname() fails, errno is set
to indicate the error.
The fdevname_r() function returns 0 if
successful. Otherwise an error number is returned.
EXAMPLES
The following code fragment determines the name of the cloned tun(4) device that is created by opening /dev/tun.
int fd;
struct stat st;
fd = open("/dev/tun", O_RDONLY);
fstat(fd, &st);
printf("devname is /dev/%s\n", devname(st.st_rdev, S_IFCHR));
printf("fdevname is /dev/%s\n", fdevname(fd));
close(fd);
ERRORS
The fdevname() and
fdevname_r() functions may fail and return the
following error codes:
- [
EBADF] - The fd is not a valid open file descriptor.
- [
EINVAL] - The fd must belong to a character device.
The fdevname_r() function may fail and
return the following error code:
- [
ERANGE] - The len argument is smaller than the length of the string to be returned.
SEE ALSO
HISTORY
The devname() function appeared in
4.4BSD.
The devname_r() function appeared in
DragonFly 1.0 and the
fdevname() and fdevname_r()
functions appeared in DragonFly 2.3.