Section (3) makedev
makedev, major, minor — manage a device number
||unsigned int maj,|
|unsigned int min
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.
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
For an explanation of the terms used in this section, see attributes(7).
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_minor(). The latter names are
exported, but the traditional names are more portable.
The BSDs expose the definitions for these macros via
> 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,
> no longer provides these
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