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gawk command in Linux with Examples

Last Updated : 01 Nov, 2024

The gawk command in Linux is a pattern scanning and processing language. No compilation is required, and variables can be used along with numeric functions, string functions, and logical operators.

Gawk is a utility that enables programmers to write highly compact but still effective programs as statements that define text patterns to look for in a text document, and the action to be taken every time such a match is found within a line.

Gawk can be used to:

Scan a file line by line
Split each input line into fields
Compare input line/fields to pattern
Perform action(s) on matched lines
Transform data files
Produce formatted reports
Format output lines
Perform arithmetic and string operations
Execute conditionals and loops

Syntax

gawk [POSIX / GNU style options] -f progfile [--] file ...
gawk [POSIX / GNU style options] [--] 'program' file ...

Basic gawk Command Example

By default, gawk prints every line of data from the named file:

gawk '{ print }' mobile.txt

Terminal output of the gawk command printing all lines from the mobile.txt Basic Options and Usage

Option

Description

-f progfile, --file=progfile

Read the AWK program source from the file program-file, instead of from the first command line argument

-F fs, --field-separator=fs

Use FS for the input field separator (the value of the FS predefined variable)

-v var=val, --assign=var=val

Assign the value val to the variable var, before execution of the program begins

Examples of Option Usage

Specifying field separator using -F option:

gawk -F: '{ print $1 }' /etc/passwd

Terminal output of gawk command with -F option

Using -f option to read program from a file:

gawk -F: -f mobile.txt /etc/passwd

Built-In Variables

NR: Keeps a running count of the number of input lines
NF: Keeps a count of the number of fields in the current input record
FS: Holds the field separator character
RS: It saves the record separator character at the present time
OFS: It saves the output field separator
ORS: It saves the output record separator

Example using NR:

gawk '{ print NR "-" $1 }' mobile.txt

Terminal output of gawk command using NR variable Advanced Usage Examples

Assume that we have a dataset in a file named mobile.txt:

Name    Mobile      Email
John    1234567890  john@example.com
Sunil   9876543210  sunil@example.com
Alice   5555555555  alice@example.com

1. Print lines matching a pattern:

gawk '/Sunil/ ' mobile.txt

output

2. Print specific fields:

gawk '{ print $2 }' mobile.txt

output

3. Count the number of lines in a file:

gawk 'END  NR}' mobile.txt

output Conclusion

The gawk command is actually one of the most powerful tools in Linux when it comes to text processing. The tool can scan files, process patterns, and execute many actions; it is very valuable to both system administrators and programmers. Mastering gawk will allow users to easily manipulate text data, generate reports, or automatically automate many other text-processing activities.

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