• #Basics of AWK
  • #Examples of Use
    • #printing whole file
    • #printing a column of file
    • #printing last column
    • #printing line with specific 'word'
    • #printing a specific field with special words
    • #priting more than one field
    • #printing first column of ls -l

1. It is mostly used as data extraction and reporting tools like 'sed' and 'grep'.
2. It is domain specific AWK (Aho, Weinberger, and Kernighan) is often considered a domain-specific language (DSL) because it is specifically designed for text processing and manipulation. While it is a powerful and flexible tool, it is tailored to excel in a particular domain: processing and analyzing text data. Here are some characteristics of AWK that highlight its domain-specific nature:

Certainly! I'll provide hypothetical examples of input data and the expected output for each AWK command. Please note that the actual results would depend on the content of your specific input files.

awk '{print}' filename
or
awk '{print $0}' filename

awk '{print $2}' filename

example: echo "hi there how are you| awk '{print $3}'" will print : how

awk '{print $NF}' filename

awk '/word/ {print}' filename

awk '/word/ {print $2}' filename

awk '{pring \(1,\)2}' filename

ls -l | awk '{print $1}'

Fields are seperated by spaces, what if they are not seperated by spaces, what to do then:
In such cases we use '-F' to set different delimeter or field seperater.

awk -F ':' '{print $2}' will set the delimeter to ':' which is the case for files like /etc/passwd

awk -F ':' '{print \(1,\)7}' /etc/passwd will return the username and the shell they are using in current session. 
or
awk -F: '{print \(1,\)7}' /etc/passwd will return the username and the shell they are using in current session. 

1. *Pattern Matching:* "To find a specific word 'error' in a log_file.txt and return each line which contains word 'error'"
   • **Input (log_file.txt):** ` Line 1: This is an error message. Line 2: Successful operation. Line 3: Another error occurred. `
   • *Command:* `bash awk '/error/ { print }' log_file.txt `
   • *Output:* ` This is an error message. Another error occurred. `
2. *Line/field-Oriented:*
   • **Input (data_file.txt):** ` John 25 Jane 30 Bob 22 `
   • *Command:* `bash awk '{ print $2 }' data_file.txt `
   • *Output:* ` 25 30 22 `
3. *Text Extraction and Transformation:*
   • **Input (/etc/passwd):** ` user1:x:1001:1001:User One:/home/user1:/bin/bash user2:x:1002:1002:User Two:/home/user2:/bin/bash `
   • *Command:* `bash awk -F: '{ print $1 }' /etc/passwd `
   • *Output:* ` user1 user2 `
4. *Default Variables:*
   • **Input (text_file.txt):** ` Short This line is longer. Another short line. `
   • *Command:* `bash awk 'length > 10' text_file.txt `
   • *Output:* ` This line is longer. `
5. *Built-in Functions:*
   • **Input (fruit_data.txt):** ` apple 5 banana 3 orange 7 `
   • *Command:* `bash awk '{ gsub(/apple/, "orange", $2); print }' fruit_data.txt `
   • *Output:* ` apple orange banana 3 orange 7 `
6. *Scripting Features:*
   • **Input (data.csv):** ` A 10 100 B 15 150 A 20 200 `
   • *Command:* `bash awk '\(1 == "A" { sum += \)3 } END { print sum }' data.csv `
   • *Output:* ` 300 `
7. *Command-Line Usage:*
   • **Input (log_file.txt):** ` Line 1: Successful operation. Line 2: Another successful operation. Line 3: Error in processing. `
   • *Command:* `bash awk '/success/ { print }' log_file.txt `
   • *Output:* ` Line 1: Successful operation. Line 2: Another successful operation.