DragonFly On-Line Manual Pages

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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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