Master Linux ‘sort’: Essential Options and Real-World Examples

The Linux sort command provides powerful sorting capabilities for text data. Below are the most frequently used options:

-n – number‑sort: sorts by numeric string values without converting to floating‑point numbers.

-g – general‑number‑sort: sorts by general numeric values and supports scientific notation.

-f – ignore‑case: performs case‑insensitive sorting.

-k POS1[,POS2] – key: sorts starting at field POS1; if POS2 is provided, sorting ends at POS2.

-t SEP – field‑separator: defines the column delimiter.

-r – reverse: sorts in descending order (default is ascending).

-h – human‑numeric‑sort: sorts numbers with human‑readable suffixes (e.g., 2K, 1G).

-u – unique: removes duplicate lines.

-o FILE – output: writes the sorted result to the specified file.

Common Usage Examples

1. Default (alphabetical) sorting

[guodong@proxy ~]$ cat word.txt
one
two
three
four

[guodong@proxy ~]$ sort word.txt
four
one
three
two

2. Numeric sorting

[guodong@proxy ~]$ cat num.txt
100
20
3

[guodong@proxy ~]$ sort num.txt -n
3
20
100

3. Column‑based sorting

Sorting a colon‑separated file by the third column in descending numeric order:

[guodong@proxy ~]$ cat passwd
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
... (other lines omitted)

[guodong@proxy ~]$ sort -t ':' -k 3 -nr passwd
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
... (remaining lines)

4. Human‑readable size sorting

Using du -h output and sorting with -h:

[guodong@proxy ~]$ du -h
2.0G    ./test2
4.0K    ./test3
316M    ./test
2.3G    .

[guodong@proxy ~]$ du -h | sort -hr
2.3G    .
2.0G    ./test2
316M    ./test
4.0K    ./test3

5. Sorting processes by memory usage

[guodong@proxy ~]$ ps aux | sort -gr -k 4 | head -n 5
shuanghu  1740 15.7  4.6 ... compiz
root       1304  2.1  1.9 ... /usr/bin/X ...
... (other lines omitted)

6. Removing duplicate lines

[guodong@proxy ~]$ cat word.txt
one
two
two
three
three
three
four
four
four

[guodong@proxy ~]$ sort -u word.txt
four
one
three
two

7. Writing sorted output to a file

Using the -o option instead of redirection:

[guodong@proxy ~]$ sort word.txt -o word.txt
[guodong@proxy ~]$ cat word.txt
four
one
three
two