Mastering Linux sort: Practical Options for Numeric, Human‑Readable, and Custom Sorting

The sort command sorts lines in a text file, either displaying the result on the screen or redirecting it to another file. Various command‑line options tailor the sorting behavior to different data types and requirements.

Basic Syntax

$ sort [options] file

Example file test:

$ cat test
zzz
sss
qqq
aaa
BBB
ddd
AAA

Running sort test produces an alphabetically sorted output.

1. Numeric Sorting (-n)

Use -n or --numeric-sort to sort by leading numbers.

$ cat test
22 zzz
33 sss
11 qqq
77 aaa
55 BBB

$ sort -n test
11 qqq
22 zzz
33 sss
55 BBB
77 aaa

2. Human‑Readable Numeric Sorting (-h)

Use -h or --human-numeric-sort for values like 1K, 2M, 1G.

$ cat test
2K
2G
1K
6T
1T
1G
2M

$ sort -h test
1K
2K
2M
1G
2G
1T
6T

3. Month Sorting (-M)

Use -M or --month-sort to order month abbreviations (jan, feb, …). At least three characters are required for each month name.

$ cat test
sept
aug
jan
oct
apr
feb
mar11

$ sort -M test
jan
feb
mar11
apr
aug
sept
oct

4. Check If Already Sorted (-c)

Use -c or --check to verify sorting; it reports the first disorder.

$ cat test
2
5
1
6

$ sort -c test
sort: test:3: disorder: 1

5. Reverse and Unique Output (-r, -u)

-r or --reverse reverses the order; -u removes duplicate lines.

$ cat test
5
2
2
1
4
4

$ sort -r test
5
4
4
2
2
1

$ sort -r -u test
5
4
2
1

6. Field‑Based and Custom Delimiter Sorting (-k, -t, -o)

Use -k to sort by a specific column, -t to define a custom delimiter, and -o to write output to a file.

$ cat test
aa aa zz
aa aa ff
aa aa tt
aa aa kk

$ sort -k3 test
aa aa ff
aa aa kk
aa aa tt
aa aa zz

With a pipe delimiter:

$ cat test
aa|5a|zz
aa|2a|ff
aa|1a|tt
aa|3a|kk

$ sort -n -t '|' -k2 test -o outfile

Resulting outfile:

$ cat outfile
aa|1a|tt
aa|2a|ff
aa|3a|kk
aa|5a|zz