20 AWK command Interview Questions and Answers

The AWK command is a powerful text processing tool that is commonly used by developers and system administrators. When applying for a position that involves text processing, it is likely that you will be asked questions about the AWK command. In this article, we discuss the most commonly asked questions about the AWK command and how you should respond.

AWK command Interview Questions and Answers

Here are 20 commonly asked AWK command interview questions and answers to prepare you for your interview:

1. What is AWK?

AWK is a command line utility that allows you to perform operations on files based on patterns that you specify. It is commonly used for things like extracting data from log files or performing calculations on large data sets.

2. Can you explain the history of AWK and who developed it?

AWK was developed in the 1970s by Alfred Aho, Peter Weinberger, and Brian Kernighan. It was designed as a tool for text processing and manipulation, and it is still widely used today for that purpose.

3. What are some important features provided by AWK?

AWK is a powerful text processing tool that provides features for manipulating and analyzing text files. Some important features provided by AWK include the ability to perform complex pattern matching, to perform arithmetic and string operations on text data, and to generate reports based on text data.

4. How do you run an awk script in Linux?

You can run an awk script in Linux by using the awk command followed by the name of the script. For example, if you have a script named “myscript.awk”, you would run it like this:

awk -f myscript.awk

5. What’s the difference between using single quotes and double quotes when executing an AWK command?

Single quotes will cause the entire string to be treated as a literal, while double quotes allow for variable interpolation. This means that if you have a variable inside of a double-quoted string, the value of that variable will be substituted in before the string is executed.

6. Is it possible to write a custom function in AWK? If yes, then how?

Yes, it is possible to write a custom function in AWK. You can do this by using the “function” keyword, followed by the name of your function, and then listing the parameters that the function will take. The body of the function will go inside of curly braces.

7. Can you explain what BEGIN and END blocks do in AWK scripts?

BEGIN and END blocks are used to specify code that should be run at the beginning and end of an AWK script, respectively. This can be useful for initializing variables or performing cleanup tasks.

8. What does the -F option do in AWK?

The -F option in AWK allows you to specify a field separator. This is useful if you have a file that is not formatted in the usual way, or if you want to parse out only certain fields from a file. For example, if you have a file with tab-separated values, you could use -F’\t’ to tell AWK to use tabs as the field separator.

9. I need to print the value of a variable in my AWK script. How can I get this done?

You can print the value of a variable in your AWK script by using the print command followed by the variable name. For example, if you have a variable named “myVar” that you want to print, you would use the following command:

print myVar

10. Can you give me some examples of common use cases for AWK commands?

AWK is a powerful command line tool that can be used for a variety of tasks. Some common use cases for AWK include extracting data from log files, manipulating CSV files, and performing calculations on large data sets.

11. Why would I want to disable auto-splitting of fields in AWK?

By default, the AWK command will automatically split fields based on whitespace. However, there may be times when you want to disable this behavior. For example, if your data contains whitespace as part of the field, then you will need to disable auto-splitting in order to preserve that data.

12. Can you explain what input redirection is in the context of AWK?

Input redirection is a way of telling the AWK command to take its input from a file or another source, instead of from the keyboard. This is useful if you have a large amount of data that you need to process and don’t want to have to type it all out by hand.

13. Can you explain the different types of loops that are available in AWK?

The three main types of loops available in AWK are the while loop, the do-while loop, and the for loop. The while loop will execute a given set of commands as long as a certain condition is met. The do-while loop is similar, but it will execute the commands at least once before checking the condition. The for loop will execute a given set of commands a certain number of times, as specified by the user.

14. When should we use pattern matching with AWK?

Pattern matching is most useful when you want to find a specific string or pattern within a file. For example, you might use pattern matching to search for all lines in a file that contain the word “ERROR”.

15. Can you name some AWK control flow statements?

Some AWK control flow statements include if/else, for, while, and do/while. These statements allow you to control the flow of execution in your AWK scripts, and can be used to perform different actions based on different conditions.

16. Can you explain what array functions are in AWK?

Array functions are a type of function that is specifically designed to work with arrays. There are a number of different array functions in AWK, each of which performs a different task. Some of the more common array functions include functions for finding the minimum or maximum value in an array, for sorting an array, and for calculating the average value of an array.

17. How do you convert one string into another using AWK?

You can use the gsub() function to convert one string into another. For example, to convert all occurrences of the string “foo” into “bar”, you would use the following command:

awk ‘{gsub(“foo”,”bar”)}1’

18. What is the best way to sum up all elements of an array in AWK?

The best way to sum up all elements of an array in AWK is to use the “for” loop command. This will allow you to iterate through all of the elements in the array and add them up as you go.

19. What happens if an expression evaluates to NULL or 0 in AWK?

If an expression evaluates to NULL or 0 in AWK, then the expression is treated as false.

20. What are regular expressions and why are they used in AWK?

Regular expressions are a way of describing patterns in text. They are often used for searching or manipulating text, and AWK uses them to match patterns in input data and perform the corresponding actions.