Awk stands for Aho Weinberger and Kernighan. Awk is a scripting language to process and analyze files.
Some of the features of Awk are given below :
- Awk actually work on data files.
- Awk can generate formatted output.
- Awk support different regular expressions.
- Awk allows different features of traditional programming language like conditions, operators, loop , functions and so on.
Syntax of Awk command
- awk 'program' input_file
The simplest program is the sequence of actions. Each action has either pattern or no pattern. Each action is enclosed with braces. We explain with a typical file named input.txt that contains name , age and height like this :
- Mehedi 01 WDE 25000
- Arafat 02 WDE 27000
- Baki 03 SDE 30000
- Mahbub 04 ADE 29000
- Nazmul 05 SDE 24000
If action has pattern , then matches that pattern with files line by line until end of file and print the matches lines. Example :
- awk '$4>=25000 {print $1, $2 }' in.txt
Output are given below
- Mehedi 01
- Arafat 02
- Baki 03
- Mahbub 04
Otherwise, action is performed for all lines of input file.
- awk '{print $1, $2 }' in.txt
Output are given below :
- Mehedi 01
- Arafat 02
- Baki 03
- Mahbub 04
- Nazmul 05
We can also write program that has only pattern and action is missing. For these programs the matched line is printed. But it is not a good practice to write only pattern without action.
- awk '/WDE/' in.txt
Output :
- Mehedi 01 WDE 25000
- Arafat 02 WDE 27000
Some points about printing :
- At the time of printing the all field of input lines we just write print.
- awk '{print }' in.txt
- Otherwise we write print and particular column number with dollar sign like $1. For more column we obviously use comma as a separator.
- awk '{print $1, $2 }' in.txt
