🧠 AWK Command Cheatsheet
awk is a powerful text-processing tool in Unix/Linux, perfect for manipulating data in files or command output. It's often used for reporting, filtering, and transforming structured text.
📦 What is AWK?
- Processes input line-by-line
- Splits each line into fields using a delimiter
- Executes actions based on optional patterns
Syntax:
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📐 Basic Examples
🔹 Print all lines
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📤 Output:
🔹 Print first column
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📤 Output:
🔍 Using Patterns
🔹 Match a specific string
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✅ Filters lines containing "error".
🔹 Match column value
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✅ Prints lines where second column value is greater than 50.
🔣 Field & Line Handling
| Variable | Description |
|---|---|
$0 | Entire line |
$1,$2 | Fields |
NF | Number of fields in current line |
NR | Current line number |
FS | Input field separator |
OFS | Output field separator |
🔹 Print number of fields
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🔹 Print last field
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🧮 Calculations
🔹 Sum a column
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📤 Output:
🔹 Average
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📤 Output:
📌 Conditionals
🔹 If-else
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📤 Output:
🔃 With Delimiters
🔹 Set delimiter (CSV)
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✅ Extracts specific fields from a comma-separated file.
🔹 Change output delimiter
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🔁 Loops
🔹 Print all fields in one column
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🧪 BEGIN & END Blocks
🔹 Add header and footer
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📤 Output:
🧰 Practical Use Cases
📁 Disk usage summary
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✅ Lists partition name and usage %.
🔍 Search logs for 404
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✅ Filters out 404 HTTP status codes.
🧹 Remove empty lines
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⚠️ Common Errors
| Error | Reason | Fix Example |
|---|---|---|
awk: syntax error | Missing quotes or braces | '...' |
awk: can't open file | File does not exist or permission error | check path |
| Fields not splitting | Wrong delimiter | use -F |
✅ Summary
AWK is a must-know for anyone working with structured text. Use it for filtering, field extraction, simple math, and formatted reporting.
📚 Want more?
man awk- GNU
gawkfor extended capabilities - awk.dev