2faeeff4c9
Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe.
143 lines
5.0 KiB
Groff
143 lines
5.0 KiB
Groff
.\" 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 likelyhood 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_reserved
|
|
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
|
|
parameter 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 .
|