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Diffstat (limited to 'lib/libc/sys/uuidgen.2')
| -rw-r--r-- | lib/libc/sys/uuidgen.2 | 142 |
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diff --git a/lib/libc/sys/uuidgen.2 b/lib/libc/sys/uuidgen.2 new file mode 100644 index 0000000..9c90102 --- /dev/null +++ b/lib/libc/sys/uuidgen.2 @@ -0,0 +1,142 @@ +.\" Copyright (c) 2002 Marcel Moolenaar +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES +.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, +.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT +.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd May 26, 2002 +.Dt UUIDGEN 2 +.Os +.Sh NAME +.Nm uuidgen +.Nd generate universally unique identifiers +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/uuid.h +.Ft int +.Fn uuidgen "struct uuid *store" "int count" +.Sh DESCRIPTION +The +.Fn uuidgen +system call generates +.Fa count +universally unique identifiers (UUIDs) and writes them to the buffer +pointed to by +.Fa store . +The identifiers are generated according to the syntax and semantics of the +DCE version 1 variant of universally unique identifiers. +See below for a more in-depth description of the identifiers. +When no IEEE 802 +address is available for the node field, a random multicast address is +generated for each invocation of the system call. +According to the algorithm of generating time-based UUIDs, this will also +force a new random clock sequence, thereby increasing the likelihood for +the identifier to be unique. +.Pp +When multiple identifiers are to be generated, the +.Fn uuidgen +system call will generate a set of identifiers that is dense in such a way +that there is no identifier that is larger than the smallest identifier in the +set and smaller than the largest identifier in the set and that is not already +in the set. +.Pp +Universally unique identifiers, also known as globally unique identifiers +(GUIDs), have a binary representation of 128-bits. +The grouping and meaning of these bits is described by the following +structure and its description of the fields that follow it: +.Bd -literal +struct uuid { + uint32_t time_low; + uint16_t time_mid; + uint16_t time_hi_and_version; + uint8_t clock_seq_hi_and_reserved; + uint8_t clock_seq_low; + uint8_t node[_UUID_NODE_LEN]; +}; +.Ed +.Bl -tag -width ".Va clock_seq_hi_and_reserved" +.It Va time_low +The least significant 32 bits of a 60-bit timestamp. +This field is stored in the native byte-order. +.It Va time_mid +The least significant 16 bits of the most significant 28 bits of the 60-bit +timestamp. +This field is stored in the native byte-order. +.It Va time_hi_and_version +The most significant 12 bits of the 60-bit timestamp multiplexed with a 4-bit +version number. +The version number is stored in the most significant 4 bits of the 16-bit +field. +This field is stored in the native byte-order. +.It Va clock_seq_hi_and_reserved +The most significant 6 bits of a 14-bit sequence number multiplexed with a +2-bit variant value. +Note that the width of the variant value is determined by the variant itself. +Identifiers generated by the +.Fn uuidgen +system call have variant value 10b. +the variant value is stored in the most significant bits of the field. +.It Va clock_seq_low +The least significant 8 bits of a 14-bit sequence number. +.It Va node +The 6-byte IEEE 802 (MAC) address of one of the interfaces of the node. +If no such interface exists, a random multi-cast address is used instead. +.El +.Pp +The binary representation is sensitive to byte ordering. +Any multi-byte field is to be stored in the local or native byte-order and +identifiers must be converted when transmitted to hosts that do not agree +on the byte-order. +The specification does not however document what this means in concrete +terms and is otherwise beyond the scope of this system call. +.Sh RETURN VALUES +.Rv -std +.Sh ERRORS +The +.Fn uuidgen +system call can fail with: +.Bl -tag -width Er +.It Bq Er EFAULT +The buffer pointed to by +.Fa store +could not be written to for any or all identifiers. +.It Bq Er EINVAL +The +.Fa count +argument is less than 1 or larger than the hard upper limit of 2048. +.El +.Sh SEE ALSO +.Xr uuidgen 1 , +.Xr uuid 3 +.Sh STANDARDS +The identifiers are represented and generated in conformance with the DCE 1.1 +RPC specification. +The +.Fn uuidgen +system call is itself not part of the specification. +.Sh HISTORY +The +.Fn uuidgen +system call first appeared in +.Fx 5.0 . |
