Using Awk for Text Processing in Linux

Awk Mental Model

Awk reads input line by line, splits it into fields, then runs actions on patterns. Think: pattern { action }.

echo "Ada Lovelace" | awk '{{print $2, $1}}'

Fields and Separators

Default field separator is whitespace. Change it with -F or by setting FS.

awk -F, '{{print $1 " -> " $3}}' data.csv

Built in Variables

• NR current record number
• NF number of fields
• $0 whole line

awk '{{print NR, NF, $0}}' file.txt

Conditions and Filtering

awk '$3 > 90 {{print $1, $2}}' scores.txt

Math and Aggregations

awk -F, '{{sum+=$3}} END {{print "Total:", sum}}' sales.csv

Format Output

awk -F: '{{printf "%-20s %s\n", $1, $7}}' /etc/passwd

Small Scripts

Awk one liners grow up fast. Put logic in a file for reuse.

cat normalize.awk
/^\s*#/ {{next}}          # skip comments
{{gsub(/\s+/, " ")}}      # collapse spaces
{{print tolower($0)}}

awk -f normalize.awk input.txt

Awk vs Grep vs Sed

Use grep to find, sed to replace, awk to compute. They are teammates, not rivals.