major(3) - f39

1makedev(3)                 Library Functions Manual                 makedev(3)
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NAME

6       makedev, major, minor - manage a device number
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <sys/sysmacros.h>
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14       dev_t makedev(unsigned int maj, unsigned int min);
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16       unsigned int major(dev_t dev);
17       unsigned int minor(dev_t dev);
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DESCRIPTION

20       A device ID consists of two parts: a major ID, identifying the class of
21       the device, and a minor ID, identifying a specific instance of a device
22       in that class.  A device ID is represented using the type dev_t.
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24       Given major and minor device IDs, makedev() combines these to produce a
25       device ID, returned as the function result.   This  device  ID  can  be
26       given to mknod(2), for example.
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28       The  major()  and  minor() functions perform the converse task: given a
29       device ID, they return, respectively, the major and  minor  components.
30       These macros can be useful to, for example, decompose the device IDs in
31       the structure returned by stat(2).
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ATTRIBUTES

34       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
35       tributes(7).
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37       ┌────────────────────────────────────────────┬───────────────┬─────────┐
38       │Interface                                   │ Attribute     │ Value   │
39       ├────────────────────────────────────────────┼───────────────┼─────────┤
40       │makedev(), major(), minor()                 │ Thread safety │ MT-Safe │
41       └────────────────────────────────────────────┴───────────────┴─────────┘
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VERSIONS

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

47       None.
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HISTORY

50       BSD, HP-UX, Solaris, AIX, Irix.
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52       These  interfaces  are defined as macros.  Since glibc 2.3.3, they have
53       been  aliases  for  three  GNU-specific  functions:  gnu_dev_makedev(),
54       gnu_dev_major(),  and  gnu_dev_minor().  The latter names are exported,
55       but the traditional names are more portable.
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57       Depending on the version, glibc  also  exposes  definitions  for  these
58       macros  from <sys/types.h> if suitable feature test macros are defined.
59       However, this behavior was deprecated in glibc 2.25,  and  since  glibc
60       2.28, <sys/types.h> no longer provides these definitions.
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