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AWK

The awk command in Linux is a powerful tool for processing text files, particularly those formatted as columns of data. It’s a scripting language that’s designed for text processing and is included by default in most Unix-like operating systems.

Here are some of the things you can do with awk:

  • Print Columns: The most basic use of awk is to print columns of data. For example, if you have a file called data.txt with the following content:
  • John 25 Engineer
    Jane 28 Doctor
  • You can print the first column (names) with the following command:
  • awk '{print $1}' data.txt

    Output:

    John
    Jane
  • Filter Rows: You can use awk to filter rows based on some condition. For example, to print only the rows where the second column (age) is greater than 26:
  • awk '$2 > 26' data.txt

    Output:

    Jane 28 Doctor
  • Perform Calculations: awk can perform calculations on the data. For example, to add 5 to the age of each person:
  • awk '{$2 = $2 + 5; print}' data.txt

    Output:

    John 30 Engineer
    Jane 33 Doctor
  • Text Substitution: You can use awk to substitute text. For example, to replace “Engineer” with “Software Engineer”:
  • awk '{gsub("Engineer","Software Engineer"); print}' data.txt

    Output:

    John 25 Software Engineer
    Jane 28 Doctor
  • Pattern Matching: awk can also perform pattern matching. For example, to print lines that contain “Doctor”:
  • awk '/Doctor/ {print}' data.txt

    Output:

    Jane 28 Doctor
  • Multiple Commands: You can use multiple commands in a single awk script. For example, to print the names of people who are not doctors:
  • awk '!/Doctor/ {print $1}' data.txt

    Output:

    John
  • Built-in Variables: awk has several built-in variables. For example, NF (number of fields) represents the number of columns. To print the last column of each row:
  • awk '{print $NF}' data.txt

    Output:

    Engineer
    Doctor
  • User-Defined Variables: You can define your own variables in awk. For example, to calculate the average age:
  • awk '{total += $2; count++} END {print total/count}' data.txt

    Output:

    26.5
  • Functions: awk supports several built-in functions. For example, length returns the length of a string. To print the length of each name:
  • awk '{print length($1)}' data.txt

    Output:

    4
    4
  • Passing Variables: You can pass variables to awk using the -v option. For example, to print rows where the age is greater than a certain value:
  • awk -v age=26 '$2 > age' data.txt

    Output:

    Jane 28 Doctor
  • File Processing: awk can process multiple files. For example, if you have another file data2.txt:
  • Alice 30 Lawyer
    Bob 35 Engineer

    You can print the names from both files:

    awk '{print $1}' data.txt data2.txt

    Output:

    John
    Jane
    Alice
    Bob
  • Complex Conditions: awk supports complex conditions. For example, to print rows where the name starts with ‘J’ and the age is less than 30:
  • awk '/^J/ && $2 < 30' data.txt

    Output:

    John 25 Engineer
    Jane 28 Doctor

    These examples should give you a good idea of the power and flexibility of awk. It’s a very versatile tool for text processing in Linux.

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