AWK cheatsheet

Ever since I started using awk in vcs I've been finding about its power but I'm unable to remember its syntax so here's a series of notes.

General notes:

• Use mawk instead of gawk when trying syntax for better cross-compatibility. Debian also has original-awk.
• Non-GNU awk doesn't understand Perl Regexes
• -F defines the field separator
• Profiling can be done with pgawk which produces an awkprof.out file with execution numbers for each statement

Books:

• Gawk: Effective AWK Programming (FSF)
• sed & awk, 2nd Edition (O'Reilly)

• cut: cut -d: -f2 ⇒ awk -F: '{ print $2 }'
• grep: grep REGEX ⇒ awk /REGEX/
  • (GNU -also in FreeBSD-) grep appears to understand Perl character classes (i.e. \w)
• grep -v: grep -v REGEX ⇒ awk '! /REGEX/'
  • Equivalent sed: sed /REGEX/ d

sub() and gsub(). Either strings or regexs can be used

$ echo hello world | awk 'sub("hello", "bye")'
> bye world

• Prepend to each line: sed 's/^/PREP: /' ⇒ awk 'sub(“”, “PREP: ”)' or awk 'sub(/^/, “PREP: ”)'

    $ echo -e 'hello\nbye' | awk 'sub(/^/, "PREP: ")'
    > PREP: hello
    > PREP: bye

• Append to each line: sed 's/$/: APP/' ⇒ awk 'sub(/$/, “: APP”)'

    $ echo -e 'hello\nbye' | awk 'sub(/$/, ": APP")'
    > hello: APP
    > bye: APP