# phpman > man > uuidgen(1)

> **TLDR:** Generate unique identifiers (UUIDs).
>
- Create a random UUIDv4:
  `uuidgen {{-r|--random}}`
- Create a UUIDv1 based on the current time:
  `uuidgen {{-t|--time}}`
- Create a UUIDv5 of the name with a specified namespace prefix:
  `uuidgen {{-s|--sha1}} {{-n|--namespace}} {{@dns|@url|@oid|@x500}} {{-N|--name}} {{object_name}}`

*Source: tldr-pages*

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[UUIDGEN(1)](https://www.chedong.com/phpMan.php/man/UUIDGEN/1/markdown)                                  User Commands                                 [UUIDGEN(1)](https://www.chedong.com/phpMan.php/man/UUIDGEN/1/markdown)



## NAME
       uuidgen - create a new UUID value

## SYNOPSIS
       **uuidgen** [options]

## DESCRIPTION
       The **uuidgen** program creates (and prints) a new universally unique identifier (UUID) using the
       [**libuuid**(3)](https://www.chedong.com/phpMan.php/man/libuuid/3/markdown) library. The new UUID can reasonably be considered unique among all UUIDs created
       on the local system, and among UUIDs created on other systems in the past and in the future.

       There are three types of UUIDs which **uuidgen** can generate: time-based UUIDs, random-based
       UUIDs, and hash-based UUIDs. By default **uuidgen** will generate a random-based UUID if a
       high-quality random number generator is present. Otherwise, it will choose a time-based UUID.
       It is possible to force the generation of one of these first two UUID types by using the
       **--random** or **--time** options.

       The third type of UUID is generated with the **--md5** or **--sha1** options, followed by **--namespace**
       _namespace_ and **--name** _name_. The _namespace_ may either be a well-known UUID, or else an alias to
       one of the well-known UUIDs defined in RFC 4122, that is **@dns**, **@url**, **@oid**, or **@x500**. The _name_
       is an arbitrary string value. The generated UUID is the digest of the concatenation of the
       namespace UUID and the name value, hashed with the MD5 or SHA1 algorithms. It is, therefore,
       a predictable value which may be useful when UUIDs are being used as handles or nonces for
       more complex values or values which shouldn’t be disclosed directly. See the RFC for more
       information.

## OPTIONS
### -r --random
           Generate a random-based UUID. This method creates a UUID consisting mostly of random
           bits. It requires that the operating system has a high quality random number generator,
           such as _/dev/random_.

### -t --time
           Generate a time-based UUID. This method creates a UUID based on the system clock plus the
           system’s ethernet hardware address, if present.

### -h --help
           Display help text and exit.

### -V --version
           Display version information and exit.

### -m --md5
           Use MD5 as the hash algorithm.

### -s --sha1
           Use SHA1 as the hash algorithm.

### -n --namespace
           Generate the hash with the _namespace_ prefix. The _namespace_ is UUID, or '@ns' where "ns"
           is well-known predefined UUID addressed by namespace name (see above).

### -N --name
           Generate the hash of the _name_.

### -x --hex
           Interpret name _name_ as a hexadecimal string.

## CONFORMING TO
       OSF DCE 1.1

## EXAMPLES
       uuidgen --sha1 --namespace @dns --name "www.example.com"

## AUTHORS
       **uuidgen** was written by Andreas Dilger for [**libuuid**(3)](https://www.chedong.com/phpMan.php/man/libuuid/3/markdown).

## SEE ALSO
       [**libuuid**(3)](https://www.chedong.com/phpMan.php/man/libuuid/3/markdown), RFC 4122 <<https://tools.ietf.org/html/rfc4122>>

## REPORTING BUGS
       For bug reports, use the issue tracker at <https://github.com/karelzak/util-linux/issues>.

## AVAILABILITY
       The **uuidgen** command is part of the util-linux package which can be downloaded from Linux
       Kernel Archive <<https://www.kernel.org/pub/linux/utils/util-linux/>>.



util-linux 2.37.2                            2021-06-02                                   [UUIDGEN(1)](https://www.chedong.com/phpMan.php/man/UUIDGEN/1/markdown)