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makedev(3) — Linux manual page

makedev(3)               Library Functions Manualmakedev(3)

NAME        top

       makedev, major, minor - manage a device number

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#include <sys/sysmacros.h>dev_t makedev(unsigned intmaj, unsigned intmin);unsigned int major(dev_tdev);unsigned int minor(dev_tdev);

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 typedev_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 tomknod(2), for example.       Themajor() andminor() 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 bystat(2).

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │Interface│Attribute│Value│       ├──────────────────────────────────────┼───────────────┼─────────┤       │makedev(),major(),minor()          │ Thread safety │ MT-Safe │       └──────────────────────────────────────┴───────────────┴─────────┘

VERSIONS        top

       The BSDs expose the definitions for these macros via<sys/types.h>.

STANDARDS        top

       None.

HISTORY        top

       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(), andgnu_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        top

mknod(2),stat(2)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17makedev(3)

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

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