makedev(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

MAKEDEV(3)              Linux Programmer's Manual             MAKEDEV(3)

NAME         top

       makedev, major, minor - manage a device number

SYNOPSIS         top

       #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);

DESCRIPTION         top

       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         top

       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         top

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

NOTES         top

       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.

SEE ALSO         top

       mknod(2), stat(2)

COLOPHON         top

       This page is part of release 5.12 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-03-22                     MAKEDEV(3)

Pages that refer to this page: mknod(2)stat(2)udev_device_new_from_syspath(3)system_data_types(7)