Open Source Software

major(3)



NAME

   makedev, major, minor - manage a device number

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

CONFORMING TO

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

NOTES

   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>, and
   glibc also exposes definitions for these macros from that  header  file
   if suitable feature test macros are defined.

SEE ALSO

   mknod(2), stat(2)

COLOPHON

   This  page  is  part of release 4.09 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/.



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