cut - Extract Section From Each Line

The cut command is used to extract specific fields or character positions from each line of input. It is especially useful for processing text files, logs, or command output where you need to isolate columns or substrings.

Essential Options

Examples

Use this sample file: employee.txt

ID,Name,Department,Salary,Location
1,Alice,Engineering,85000,New York
2,Bob,Sales,65000,San Francisco
3,Charlie,HR,60000,Chicago
4,David,Engineering,90000,Boston
5,Eva,Marketing,70000,Seattle

1. Extracting fields by delimiter

cut -d',' -f2 emp.txt

2. Extract name and salary

cut -d',' -f2,4 emp.txt

3. Extract the first 3 characters of each line

cut -c1-3 emp.txt

4. Skip the header and extract “Deparment” and “Location”

cat emp.txt | cut -d',' -f3,5

5. Replace output delimiter with : instead of ,

cut -d',' -f1,2 --output-delimiter=':' emp.txt

6. Display everything except the ID

cut -d ',' -f1 --complement emp.txt

sort - Sort Lines Of Text Files

The sort command arranges lines in text files in alphabetical, numerical or custom column-based order. It’s a powerful tool for organizing data, finding duplicates, and preparing files for further processing.

Essential Options

Examples

Use this sample file: emp.csv

OrderID,Customer,Amount,Date
1003,Alice,250,2025-07-01
1001,Bob,100,2025-06-29
1005,Charlie,300,2025-07-03
1002,Eva,150,2025-06-30
1004,David,100,2025-07-02

1. Sort by Amount (3rd Column) numerically

sort -t ',' -k3,3 -n emp.csv

We need to separate the fields in order to access the 3rd column,

• Use -t "," to specifiy delimiter which separates the lines with ,(comma) as delimiter.
• Then we specify -k3,3 which selects the 3rd column (because the fields are separated)
• and finally, we can sort it numerically by using -n.

2. Sort by Date (4th column) alphabetically

sort -t ',' -k4,4 emp.csv #sort alphabetically by default

3. Sort by Customer Name (2nd column) in reverse order

sort -t ',' -k2,2 -r emp.csv

4. Remove duplicate lines while sorting by amount

sort -t ',' -k3,3 -u emp.csv

5. Sort by OrderID (1st column) numerically

sort -t ',' -k1,1 -n emp.csv

uniq - Report Or Filter Repeated Lines

The uniq command is used to remove duplicate adjacent lines from a file or output. It is most effective when used after sort, as only consecutive duplicate lines are filtered.

Essential Options

Examples

Use this sample file: hosts.txt

server1.example.com
server2.example.com
server1.example.com
server3.example.com
server2.example.com
server2.example.com
server4.example.com
server5.example.com
server5.example.com
server5.example.com

1. Show unique hostnames

sort hosts.txt | uniq

2. Count occurrences of each hostname

sort hosts.txt | uniq -c

3. Show only hostnames that appear more than once

sort hosts.txt | uniq -d

4. Show only hostnames that appear exactly once

sort hosts.txt | uniq -u

tr - Translate or Delete Characters

The tr command is used to translate (replace), squeeze, or delete characters from standard input. It’s great for quick, in-place text transformations.

Essential Options

Examples

1. Convert all lowercase letters to uppercase letters

echo "Hello Bro!" | tr 'a-z' 'A-Z'

2. Delete all digits from input

echo "abc123" | tr -d '0-9'

3. Squeeze multiple spaces into single space

echo "a     b       c" | tr -s ' '

4. Replace commas with tabs

echo "a,b,c" | tr ',' '\t'