GUID

Globally Unique ID generator

Usability

When you need to generate an unique string with very low probability of being duplicated worldwide, from eg. a Linux (or other) bash script. The uniqueness is maintained by combining entropy from several sources (/dev/random, IRQ counters at /proc/interrupts, current date/time, and the packet counters on the network interfaces) and fixed machine-specific information (the MAC addresses of the network interfaces from the ifconfig -a output), which is mixed up together with the other data using a hash function, so there are no privacy implications as the MAC address can't be recovered from the GUID.

Purpose

Whenever a reliably unique identifier is necessary to be assigned to some data object. The object may be a database object, a file, or an identifier of a webpage (eg. to allow finding the resource by a search engine when its URL changes but the GUID embedded in its source is known). The GUID string is broken to smaller parts (7 or 8 characters) to allow easier writing down.

Usage

guid - generate a global unique identifier based on a hash of the machine
   network hardware (ifconfig -a), timestamp, IRQ counter and 16 random bytes.
Usage: guid [-s|-m] [-b|-x] [-S <separator>]
where: -s sets 160-bit GUID (SHA1)
       -m sets 128-bit GUID (MD5, default)
       -b sets output in BASE64 encoding
       -X sets output in uppercase HEX
       -x sets output in lowercase HEX (default)
       -S sets <separator> (default '-')
       -h writes this help

Example outputs:

`guid -s -x`	:	`863da6a8-7be66589-4a21f83b-e1620008-8d2b939e`
`guid -m -X`	:	`A1051E41-9633ACE1-87215E24-6A9196FB`
`guid -s -b`	:	`ByNeoOj-zbPcDPK-PyWi2md-pQik0M`
`guid -m -b`	:	`YqU0b1b7-6H8Qy3f-AEh9JQA`

Requires

md5sum and sha1sum - should be part of any standard distro
base64 - a base64 encoder, could be downloaded eg. here

Files

guid - shell script