gawk - pattern scanning and processing language

Options you will use

-F SEP

Input field separator. -F: for /etc/passwd, -F, for CSV.

-v VAR=VAL

Set a variable before the program runs.

'PATTERN {ACTION}'

Run ACTION on every line matching PATTERN. Either may be omitted.

BEGIN / END

Blocks that run before the first line and after the last.

$0 $1 $N NF NR FS OFS

Whole line, fields, field count, record number, separators.

Examples

$ awk -F: '$3 >= 1000 {print $1}' /etc/passwd

real login users - and the surprise: nobody has UID 65534

$ awk '{sum+=$10} END {print sum}' access.log

total bytes served

$ awk '$9 ~ /^5/ {c[$1]++} END {for (ip in c) print c[ip], ip}' access.log | sort -rn

who is causing the 5xx

$ awk '{s+=$NF} END {printf "%.3f\n", s/NR}'

average of the last field

Gotchas

• awk splits on runs of whitespace by default, which is exactly what cut cannot do.