Table of Contents
AWK is suitable for pattern search and processing. The script runs to search one or more files to identify matching patterns and if the said patterns perform specific tasks. In this guide, we take a look into AWK Linux command and see what it can do.
What Operations can AWK do?
- Scanning files line by line
- Splitting each input line into fields
- Comparing input lines and fields to patterns
- Performing specified actions on matching lines
AWK Command Usefulness
- Changing data files
- Producing formatted reports
Programming Concepts for awk command
- Format output lines
- Conditional and loops
- Arithmetic and string operations
AWK Syntax
awk options 'selection _criteria {action }' input-file > output-file
To demonstrate more about AWK usage, we are going to use the text file called file.txt !awk command example file 1st column => Item, 2nd column => Model 3rd column => Country 4th column => Cost
Awk Command Examples
Printing specific columns
To print the 2nd and 3rd columns, execute the command below.
awk '{print $2 "\t" $3}' file.txt
Printing all lines in a file
If you wish to list all the lines and columns in a file, execute
awk ' {print $0}' file.txt
Output !Awk Print All Lines
Printing all lines that match a specific pattern
if you want to print lines that match a certain pattern, the syntax is as shown
awk '/variable_to_be_matched/ {print $0}' file.txt
For instance, to match all entries with the letter 'o', the syntax will be
awk '/o/ {print $0}' file.txt
Output !awk linux command matching all lines To match all entries with the letter 'e'
awk '/e/ {print $0}' file.txt
Output !Awk Matching Lines With E
Printing columns that match a specific pattern
When AWK locates a pattern match, the command will execute the whole record. You can change the default by issuing an instruction to display only certain fields. For example:
awk '/a/ {print $3 "\t" $4}' file.txt
The above command prints the 3rd and 4th columns where the letter 'a' appears in either of the columns Output !Awk Matching Column
Counting and Printing Matched Pattern
You can use AWK to count and print the number of lines for every pattern match. For example, the command below counts the number of instances a matching pattern appears
awk '/a/{++cnt} END {print "Count = ", cnt}' file.txt
Output !Count Columns Matching a pattern
Print Lines with More or less than a No. of Characters
AWK has a built-in length function that returns the length of the string. From the command $0 variable stores the entire line and in the absence of a body block, the default action is taken, i.e., the print action. Therefore, in our text file, if a line has more than 18 characters, then the comparison results true, and the line is printed as shown below.
awk 'length($0) > 20' file.txt
Saving output of AWK to a different file
If you wish to save the output of your results, use the > redirection operator. For example
awk '/a/ {print $3 "\t" $4}' file.txt > Output.txt
You can verify the results using the cat command as shown below
cat output.txt
Output !Awk Redirect Output
Conclusion
AWK is another simple programming script that you can use to manipulate text in documents or perform specific functions. The shared commands are a few or the many you are yet to know or come across.
