AWK Overview
AWK is an acronym formed from the initials of its three developers: A. V. Aho, P. J. Weinberger, and B. W. Kernighan. It is a widely used data manipulation language in Unix-like systems. It reads input line by line from files or standard input and processes data based on specified patterns and actions.
How AWK Works
AWK follows a basic structure: `pattern { action }`. For each line read, if the `pattern` matches, the `action` is performed. If there is no pattern, the action is performed for every line. If there is no action, matching lines are printed as is.
Features of AWK
- Line-by-line processing: Processes input files one line (record) at a time.
- Field-level access: Divides each line into fields ($1, $2, ...) separated by whitespace (default delimiter) and allows access to them.
- Pattern matching: Can perform operations only on lines that match a specific pattern.
- Programming capabilities: Provides basic programming features such as variables, conditional statements, loops, and functions.
- Report generation: Can easily generate complexly formatted text reports.
Key AWK Commands and Options
Precisely process text data using AWK's various options, built-in variables, and special patterns.
1. Basic Usage and Input/Output Options
2. Built-in Variables
3. Special Patterns
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Usage Examples
Experience the magic of text data processing through various examples of AWK command usage.
Print only the second column from a file
awk '{print $2}' data.txtExtracts and prints only the second field (column) of each line from the `data.txt` file. (Default delimiter: space)
Print specific columns from a CSV file
awk -F',' '{print "Name: " $1 ", Score: " $3}' scores.csvPrints the name (first field) and score (third field) from the `scores.csv` file, which is comma (`,`) delimited.
Print only lines containing a specific pattern
awk '/ERROR/{print}' log.txtPrints all lines containing the string 'ERROR' from the `log.txt` file.
Print with line numbers
awk '{print NR ": " $0}' names.txtPrints each line of the `names.txt` file prefixed with its line number.
Change the second field value in lines where the first field is 'apple'
awk '$1 == "apple" {$2 = "fruit"; print}' inventory.txtFinds lines in the file where the first field is 'apple', changes the second field to 'fruit', and then prints the entire line.
Print messages before and after file processing and calculate total sum
awk 'BEGIN {total = 0; print "Calculation Starts!"} {total += $1} END {print "Total: " total}' numbers.txtAdds all numbers in `numbers.txt` and prints messages at the beginning and end. (Assumes each line contains only one number)