DragonFly On-Line Manual Pages
DEVNAME(3) DragonFly Library Functions Manual DEVNAME(3)
devname, devname_r, fdevname, fdevname_r - get device name
Standard C Library (libc, -lc)
devname(dev_t dev, mode_t type);
devname_r(dev_t dev, mode_t type, char *buf, size_t len);
fdevname_r(int fd, char *buf, size_t len);
The devname() 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.
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.
The following code fragment determines the name of the cloned tun(4)
device that is created by opening /dev/tun.
struct stat st;
fd = open("/dev/tun", O_RDONLY);
printf("devname is /dev/%s\n", devname(st.st_rdev, S_IFCHR));
printf("fdevname is /dev/%s\n", fdevname(fd));
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.
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.
DragonFly 5.9-DEVELOPMENT January 1, 2021 DragonFly 5.9-DEVELOPMENT