uuidgen —
generate universally unique identifiers
  
    | uuidgen | [ -1s] [-ncount] [-ofilename] | 
The uuidgen utility by default generates a single
  universally unique identifier (UUID), also known as a globally unique
  identifier (GUID). By default, uuidgen generates a
  single UUID and outputs it in the standard string representation to stdout.
  The following options can be used to change the behavior of
  uuidgen:
  - -1
- This option only has effect if multiple identifiers are to be generated
      and instructs uuidgento not generate them in
      batch, but one at a time.
- -ncount
- This option controls the number of identifiers generated. By default,
      multiple identifiers are generated in batch.
- -ofilename
- Redirect output to filename instead of stdout.
- -s
- Output UUIDs as initialized C structures, rather than in the standard
      string format.
 
Batched generation yields a dense set of identifiers 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.
When generating the identifiers one at a time, the identifiers
    will be close to each other, but operating system latency and processing
    time will be reflected in the distance between two successive
  identifiers.
The uuidgen utility exits 0 on success,
  and >0 if an error occurs.
The uuidgen command first appeared in
  NetBSD 3.0.