focal (3) makedev.3.gz

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>.  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

       mknod(2), stat(2)

COLOPHON

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