mirror of https://github.com/mkerrisk/man-pages
makedev.3: New page for makedev(), major(), and minor() macros
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com> Reviewed-by: Phil Endecott <phil_vonar_endecott@chezphil.org>
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.\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH MAKEDEV 3 2008-12-01 "Linux" "Linux Programmer's Manual"
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.SH NAME
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makedev, major, minor \- manage a device number
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.SH SYNOPSIS
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.nf
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.B #define _BSD_SOURCE
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.B #define <sys/types.h>
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.BI "dev_t makedev(int " maj ", int " min );
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.BI "int major(dev_t " dev );
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.BI "int minor(dev_t " dev );
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.fi
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.\" FIXME Add links
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.SH DESCRIPTION
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A device ID consists of two parts:
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a major ID, identifying the class of the device,
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and a minor ID, identifying a specific instance of a device in that class.
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A device ID is represented using the type
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.IR dev_t .
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Given major and minor device IDs,
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.BR makedev ()
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combines these to produce a device ID, returned as the function result.
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This device ID can be given to
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.BR mknod (2),
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for example.
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The
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.BR major ()
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and
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.BR minor ()
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functions perform the converse task: given a device ID,
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they return, respectively, the major and minor components.
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These macros can be useful to, for example,
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decompose the device IDs in the structure returned by
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.BR stat (2).
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.SH "CONFORMING TO"
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The
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.BR makedev ()
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.BR major ()
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and
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.BR minor ()
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functions are not specified in POSIX.1,
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but are present on many other systems.
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.\" The BSDs, HP-UX, Solaris, AIX, Irix
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.SH NOTES
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These interfaces are defined as macros.
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Since glibc 2.3.3,
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they have been aliases for three GNU-specific functions:
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.BR gnu_dev_makedev (3),
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.BR gnu_dev_major (3),
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and
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.BR gnu_dev_minor (3).
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The latter names are exported, but the traditional names are more portable.
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.SH "SEE ALSO"
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.BR mknod (2),
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.BR stat (2)
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.\" FIXME -- add SEE ALSO's from those pages.
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