shuf

What it does

shuf outputs lines or numbers in random order. It is useful for random sampling, load testing, or selecting random entries from files.

How it works (mechanical)

• Reads all input into memory.
• Randomly permutes the order.
• Outputs full shuffle or limited sample.

10 Practical Examples

# 1) Shuffle lines in a file
shuf names.txt

# 2) Pick one random line
shuf -n 1 names.txt

# 3) Pick 5 random lines
shuf -n 5 names.txt

# 4) Shuffle numbers 1–10
shuf -i 1-10

# 5) Shuffle numbers with limit
shuf -i 1-100 -n 10

# 6) Randomize server list before deployment
cat servers.txt | shuf

# 7) Random test user selection
shuf -n 1 /var/tmp/inu0users

# 8) Combine with head
shuf file.txt | head -n 3

# 9) Deterministic shuffle (seed via random-source)
shuf --random-source=seedfile file.txt

# 10) Randomize pipeline input
grep ERROR logs.txt | shuf

Notes & Gotchas

• Reads entire input into memory (large files caution).
• -n limits output count.
• -i generates numeric range.
• --random-source allows deterministic behavior.

Historical Context

Part of GNU coreutils, shuf reflects Unix’s composability philosophy: small tool, precise function, powerful when piped.

Related Commands

• sort — ordered output
• nl — line numbering
• head — limit output
• awk — programmable sampling