major (3)

Leading comments

Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
    <mtk.manpages@gmail.com>

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(The comments found at the beginning of the groff file "man3/major.3".)

NAME

makedev, major, minor - manage a device number

SYNOPSIS

#define _BSD_SOURCE             /* See feature_test_macros(7) */
#include <sys/types.h>

dev_t makedev(unsigned int maj, unsigned int min);

unsigned int major(dev_t dev);
unsigned int minor(dev_t dev);

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).

Interface	Attribute	Value
makedev(), major(), minor()	Thread safety	MT-Safe

CONFORMING TO

The makedev(), major(), and minor() functions are not specified in POSIX.1, but are present on many other systems.

NOTES

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.

SEE ALSO

mknod(2), stat(2)

COLOPHON

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