major(3)

NAME#

makedev, major, minor - manage a device number

LIBRARY#

Standard C library (libc, -lc)

SYNOPSIS#

#include <sys/sysmacros.h>

dev_t makedev(unsigned int \nmaj\n, unsigned int \nmin\n);

unsigned int major(dev_t \ndev\n);\n
\nunsigned int minor(dev_t \ndev\n);

DESCRIPTION#

A device ID consists of two parts: a major ID, identifying the class of the device, and a minor ID, identifying a specific instance of a device in that class. A device ID is represented using the type dev_t.

Given major and minor device IDs, makedev() combines these to produce a device ID, returned as the function result. This device ID can be given to mknod(2), for example.

The major() and minor() functions perform the converse task: given a device ID, they return, respectively, the major and minor components. These macros can be useful to, for example, decompose the device IDs in the structure returned by stat(2).

ATTRIBUTES#

For an explanation of the terms used in this section, see attributes(7).

VERSIONS#

The BSDs expose the definitions for these macros via <sys/types.h>.

STANDARDS#

None.

HISTORY#

BSD, HP-UX, Solaris, AIX, Irix.

These interfaces are defined as macros. Since glibc 2.3.3, they have been aliases for three GNU-specific functions: gnu_dev_makedev(), gnu_dev_major(), and gnu_dev_minor(). The latter names are exported, but the traditional names are more portable.

Depending on the version, glibc also exposes definitions for these macros from <sys/types.h> if suitable feature test macros are defined. However, this behavior was deprecated in glibc 2.25, and since glibc 2.28, <sys/types.h> no longer provides these definitions.

SEE ALSO#

mknod(2), stat(2)