How to Generate UUID in Bash

How to Generate a UUID in Bash

The standard way to generate a UUID in Bash is the uuidgen command, pre-installed on macOS (part of libuuid) and most Linux distributions (part of util-linux). Call it directly or capture the output in a variable for use elsewhere in your script. The r uuid reference explains how to use uuid::UUIDgenerate() for random v4 identifiers in R.

generate.sh

#!/bin/bash

my_uuid=$(uuidgen)
echo "$my_uuid"
# Output: 550E8400-E29B-41D4-A716-446655440000

# Normalize to lowercase (uuidgen prints uppercase on macOS, lowercase on most Linux)
echo "$my_uuid" | tr '[:upper:]' '[:lower:]'

Explanation

uuidgen ships as part of util-linux on Linux and libuuid on macOS, so it's available on almost every Unix-like system with no extra install.
my_uuid=$(uuidgen) captures the generated identifier in a shell variable using command substitution.
macOS's uuidgen typically prints uppercase hex digits while most Linux distributions print lowercase — pipe through tr '[:upper:]' '[:lower:]' to normalize the case before storing or comparing UUIDs.
With no flags, uuidgen defaults to generating a random (version 4) UUID.

Validate a UUID String in Bash

Bash has no typed UUID value, so validating a UUID string means checking that it matches the expected shape with a regular expression. The [[ ... =~ ... ]] conditional performs the match without spawning an external process. For idiomatic Kotlin UUID patterns with extension functions and sealed classes, see the kotlin uuid guide.

validate.sh

#!/bin/bash

id="550e8400-e29b-41d4-a716-446655440000"
pattern='^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$'

if [[ "$id" =~ $pattern ]]; then
    echo "valid"
else
    echo "invalid"
fi

Explanation

The pattern variable holds a regex matching the standard 36-character UUID shape: 8-4-4-4-12 hexadecimal groups separated by hyphens.
[0-9a-fA-F] matches both uppercase and lowercase hex digits directly, so there's no need to enable shopt -s nocasematch or normalize the string's case first.
[[ "$id" =~ $pattern ]] performs the match; storing the pattern in a variable rather than inlining it avoids quoting issues with the regex's special characters.
This only checks the string's shape, not its version or variant bits — a string like 00000000-0000-0000-0000-000000000000 still passes.

Other Options for Generating UUIDs in Bash

uuidgen also accepts flags for forcing a specific UUID version, and Linux offers a kernel-level fallback for systems where uuidgen isn't installed.

alternatives.sh

#!/bin/bash

# Force a random (version 4) UUID
uuidgen -r

# Force a time-based (version 1) UUID
uuidgen -t

# Kernel-level fallback on Linux -- no package required
cat /proc/sys/kernel/random/uuid

Explanation

uuidgen -r explicitly requests a random, version 4 UUID — useful when you want to be certain of the version regardless of the system default.
uuidgen -t forces a time-based, version 1 UUID, which encodes the current timestamp and a node identifier instead of pure randomness.
On Linux, cat /proc/sys/kernel/random/uuid reads a freshly generated random UUID straight from the kernel — it works even on minimal or containerized systems where uuidgen isn't installed.
The kernel-random-uuid approach is Linux-specific; it has no equivalent on macOS, so fall back to uuidgen there.

Generate UUID in Bash

How to Generate a UUID in Bash

Explanation

Validate a UUID String in Bash

Explanation

Other Options for Generating UUIDs in Bash

Explanation

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