Less

1. cat (Concatenate)

• Displays the contents of a file
• Example: cat filename.txt

2. head and tail

• Display the first or last few lines of a file

+ head: displays the first 10 lines by default, but can be customized with -n option (e.g., head -5 filename.txt) + tail: displays the last 10 lines by default, but can be customized with -n option (e.g., tail -3 filename.txt)

3. sed (Stream Editor)

• Edits text in a file using regular expressions
• Example: sed 's/old_text/new_text/g' filename.txt (replaces "old_text" with "new_text")

4. grep (Global Regular Expression Print)

• Searches for a pattern within a file and prints the matching lines
• Example: grep keyword filename.txt

5. cut

• Extracts specific fields from a file based on delimiters (e.g., space, comma)
• Example: cut -d ',' -f 1 filename.csv (extracts first field using comma as delimiter)

6. sort and uniq

• Sorts the lines of a file alphabetically or numerically

+ sort: sorts in ascending order by default; use -r option for descending order (e.g., sort -r filename.txt) + uniq: removes duplicate lines from a sorted file

7. awk

• A powerful tool for text processing that can perform actions based on conditions
• Example: awk '{print $1}' filename.txt (prints the first field of each line)

These are just a few examples, but they cover some of the most common use cases for text processing in Linux.

Example Use Case: Suppose you have a file named students.csv with the following contents:

John,20,Male
Jane,21,Female
Bob,19,Male
Alice,22,Female

You can use the above commands to perform various operations on this file. For instance:

• Display the first three lines: head -3 students.csv
• Replace "Male" with "Boy": sed 's/Male/Boy/g' students.csv
• Sort the file by age in descending order: sort -r -k 2 students.csv