The sort Command

Data is rarely in the order you want. sort fixes that.

Basic Sort

Terminal

$cat names.txt

charlie alice bob

$sort names.txt

alice bob charlie

By default, sort sorts alphabetically (by ASCII value).

Reverse Sort

Terminal

$sort -r names.txt

charlie bob alice

Numeric Sort

This is crucial. Watch the difference:

Terminal

$echo -e '10\n2\n1\n20' | sort

1 10 2 20

$echo -e '10\n2\n1\n20' | sort -n

1 2 10 20

Without -n, "10" comes before "2" because "1" < "2" alphabetically.

Always Use -n for Numbers

If you're sorting numbers and the order looks wrong, you probably forgot -n.

Sort by Column

Sort by a specific field:

Terminal

$cat scores.txt

alice 95 bob 87 charlie 92

$sort -k2 -n scores.txt

bob 87 charlie 92 alice 95

-k2 = sort by second column (key 2).

With Different Delimiters

Terminal

$cat data.csv

alice,95,engineering bob,87,marketing charlie,92,sales

$sort -t',' -k2 -n data.csv

bob,87,marketing charlie,92,sales alice,95,engineering

-t',' sets comma as delimiter.

Human-Readable Sizes

Sort file sizes like 1K, 2M, 3G:

Terminal

$du -h /var/log/* | sort -h | tail -5

4.0K /var/log/apt 100K /var/log/journal 2.5M /var/log/syslog 15M /var/log/nginx 50M /var/log/mysql

-h understands K, M, G suffixes.

Remove Duplicates

Terminal

$sort -u names.txt

(sorted and unique)

-u removes duplicate lines (same as sort | uniq).

Case-Insensitive Sort

Terminal

$echo -e 'Bob\nalice\nCharlie' | sort

Bob Charlie alice

$echo -e 'Bob\nalice\nCharlie' | sort -f

alice Bob Charlie

-f (fold case) treats upper and lowercase as equal.

Random Sort (Shuffle)

Terminal

$sort -R names.txt

(random order each time)

Great for randomizing data.

Stable Sort

Preserve original order for equal elements:

Terminal

$sort -s -k1 data.txt

(maintains relative order within same key)

Real-World Examples

Find Largest Files

Terminal

$ls -lh | sort -k5 -h -r | head

(biggest files first)

Top IP Addresses by Count

Terminal

$cut -d' ' -f1 access.log | sort | uniq -c | sort -rn | head

1523 192.168.1.1 892 10.0.0.5 234 172.16.0.1

Sort CSV by Column 3

Terminal

$sort -t',' -k3 data.csv

(sorted by third column)

Knowledge Check

Why does `sort` put '10' before '2' without the -n flag?

Quick Reference

Flag	Effect
`-n`	Numeric sort
`-r`	Reverse order
`-k N`	Sort by column N
`-t`	Set field delimiter
`-h`	Human-readable sizes
`-u`	Unique (remove duplicates)
`-f`	Case-insensitive
`-R`	Random shuffle

Key Takeaways

Default sort is alphabetical (ASCII order)
Always use -n for numbers
-k N sorts by the Nth column
-t sets the delimiter for columns
-h handles human-readable sizes (K, M, G)
-r reverses the order

Next: removing duplicates with uniq.

Sort by Column

Sort by a specific field:

Terminal

$cat scores.txt

alice 95 bob 87 charlie 92

$sort -k2 -n scores.txt

bob 87 charlie 92 alice 95

-k2 = sort by second column (key 2).

With Different Delimiters

Terminal

$cat data.csv

alice,95,engineering bob,87,marketing charlie,92,sales

$sort -t',' -k2 -n data.csv

bob,87,marketing charlie,92,sales alice,95,engineering

-t',' sets comma as delimiter.

Real-World Examples

Find Largest Files

Terminal

$ls -lh | sort -k5 -h -r | head

(biggest files first)

Top IP Addresses by Count

Terminal

$cut -d' ' -f1 access.log | sort | uniq -c | sort -rn | head

1523 192.168.1.1 892 10.0.0.5 234 172.16.0.1

Sort CSV by Column 3

Terminal

$sort -t',' -k3 data.csv

(sorted by third column)

Knowledge Check

Why does `sort` put '10' before '2' without the -n flag?

Flag

Effect

-n

Numeric sort

-r

Reverse order

-k N

Sort by column N

-t

Set field delimiter

-h

Human-readable sizes

-u

Unique (remove duplicates)

-f

Case-insensitive

-R

Random shuffle