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DEVNAME(3)            DragonFly Library Functions Manual            DEVNAME(3)


NAME

     devname, devname_r, fdevname, fdevname_r - get device name


LIBRARY

     Standard C Library (libc, -lc)


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

     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.


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

     stat(2), devfs(5)


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.

DragonFly 5.9-DEVELOPMENT       January 1, 2021      DragonFly 5.9-DEVELOPMENT

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