Text Processing

1. `grep` – Search for Patterns

Purpose: Searches for specific patterns in text using regular expressions.
Basic Usage:
```
grep "pattern" filename
```
Example:
```
grep "error" server.log
```
Finds all lines in server.log that contain the word “error”.

2. `awk` – Pattern Scanning and Processing

Purpose: A powerful programming language for pattern scanning, text manipulation, and reporting.
Basic Usage:
```
awk '{print $1}' filename
```
Example:
```
awk '/error/ {print $2}' server.log
```
Prints the second field of lines that contain “error”.

3. `sed` – Stream Editor

Purpose: Edits text in a stream, often used for substitution or deletion.
Basic Usage:
```
sed 's/old/new/' filename
```
Example:
```
sed 's/error/issue/' server.log
```
Replaces the first occurrence of “error” with “issue” in each line.

4. `cut` – Extract Columns from Text

Purpose: Removes sections (fields or columns) from each line of input.
Basic Usage:
```
cut -d':' -f1 /etc/passwd
```
Example:
Outputs the first field (username) from /etc/passwd.

5. `sort` – Sort Lines of Text Files

Purpose: Sorts lines in text files alphabetically or numerically.
Basic Usage:
```
sort filename
```
Example:
```
sort -n numbers.txt
```
Sorts numbers in ascending numerical order.

6. `uniq` – Report or Filter Repeated Lines

Purpose: Removes or displays duplicate lines (only works on sorted data).
Basic Usage:
```
uniq filename
```
Example:
```
sort data.txt | uniq -c
```
Sorts the file and shows each line’s frequency of occurrence.