makedev, major, minor - manage a device number
#include <sys/sysmacros.h>
dev_t makedev(unsigned int maj, unsigned int min);
unsigned int major(dev_t dev);
unsigned int minor(dev_t dev);
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).
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| makedev (), major (), minor () |
Thread safety |
MT-Safe |
The
makedev(),
major(), and
minor() functions are not
specified in POSIX.1, but are present on many other systems.
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.
The BSDs expose the definitions for these macros via
<sys/types.h>.
Depending on the version, glibc also exposes definitions for these macros from
that header file 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.
mknod(2),
stat(2)