makedev(3) — Linux manual page

makedev(3)              Library Functions Manual              makedev(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 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 │
       └─────────────────────────────────────┴───────────────┴─────────┘

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)

COLOPHON

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Linux man-pages 6.9.1          2024-05-02                     makedev(3)

Pages that refer to this page: mknod(2), dev_t(3type), stat(3type), udev_device_new_from_syspath(3)

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