awk

it’s often said that awk is a programming language.

awk scans over a text file, it treats each line individually and in succession, like an array. each line is a record.

each record is broken into fields.

NR → no of. records NF → no of. fields

to print no of lines in a file, run:

awk 'END { print NR; }' sample.txt

awk script have a pattern or keyword, and an action it performs when the keyword is encountered.

pattern or keyword { action }

in the previous script, we used END, which only executes at the end of the parsing data.

you can use a pattern instead, to filter results. here $0 will store the current record, i.e., the line in which a match is found.

awk '/Linux/ { print $0; }' sample.txt

$0 → current record $1 → current field (in our example, it’s “Linux”) $2 → next field (word next to “Linux”), and so on…

by default, fields are separated by spaces, but you can change that by using the -F flag. it sets the FS variable.

run man awk | awk '/(f|F)ield.*separator/ {print NR "|" $0;}' to search man documentation on field separator.

awk -F ':' [...]

here’s the function semantics in awk.

name(parameters) { action }

there are functions to perform mathematical operations and string processing.

math ones are often fairly straightforward. you provide a number, and it crunches it.

awk 'BEGIN { print sqrt(1764); }'
---
42

📝 Notes