awk or gawk (gnu awk)

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Syntax


      awk  'Program' Input-File1 Input-File2 ...


      awk -f PROGRAM-FILE  Input-File1 Input-File2 ...


Key

 -F FS

 --field-separator FS

     Use FS for the input field separator (the value of the `FS'

     predefined variable).


 -f PROGRAM-FILE

 --file PROGRAM-FILE

     Read the `awk' program source from the file PROGRAM-FILE, instead

     of from the first command line argument.


 -mf NNN

 -mr NNN

     The `f' flag sets the maximum number of fields, and the `r' flag

     sets the maximum record size.  These options are ignored by

     `gawk', since `gawk' has no predefined limits; they are only for

     compatibility with the Bell Labs research version of Unix `awk'.


 -v VAR=VAL

 --assign VAR=VAL

     Assign the variable VAR the value VAL before program execution

     begins.


 -W traditional

 -W compat

 --traditional

 --compat

     Use compatibility mode, in which `gawk' extensions are turned off.


 -W lint

 --lint

     Give warnings about dubious or non-portable `awk' constructs.


 -W lint-old

 --lint-old

     Warn about constructs that are not available in the original

     Version 7 Unix version of `awk'.


 -W posix

 --posix

     Use POSIX compatibility mode, in which `gawk' extensions are

     turned off and additional restrictions apply.


 -W re-interval

 --re-interval

     Allow interval expressions, in regexps.


 -W source=PROGRAM-TEXT

 --source PROGRAM-TEXT

     Use PROGRAM-TEXT as `awk' program source code.  This option allows

     mixing command line source code with source code from files, and is

     particularly useful for mixing command line programs with library

     functions.


 --

     Signal the end of options.  This is useful to allow further

     arguments to the `awk' program itself to start with a `-'.  This

     is mainly for consistency with POSIX argument parsing conventions.


'Program'

     A series of patterns and actions: see below


Input-File

     If no Input-File is specified then `awk' applies the Program to 

     "standard input", (piped output of some other command or the terminal.

     Typed input will continue until end-of-file (typing `Control-d')

     pattern { action }

     pattern { action }

     ...[/code]


e.g. Display lines from my_file containing the string "123" or "abc" or "some text":

awk '/123/ { print $0 } 

     /abc/ { print $0 }

     /some text/ { print $0 }' my_file

/Regular Expression/        - Match =

Pattern && Pattern          - AND

Pattern || Pattern          - OR

! Pattern                   - NOT

Pattern ? Pattern : Pattern - If, Then, Else

Pattern1, Pattern2          - Range Start - end

BEGIN                       - Perform action BEFORE input file is read

END                         - Perform action AFTER input file is read

    , { ? : || && do else

# This program prints a nice friendly message

awk '{ if (length($0) > max) max = length($0) }

      END { print max }' data

 awk 'NF > 0' data

 awk 'BEGIN { for (i = 1; i 
                print int(101 * rand()) }'

 ls -lg FILES | awk '{ x += $5 } ; END { print "total bytes: " x }'

 awk -F: '{ print $1 }' /etc/passwd | sort

 awk 'END { print NR }' data

 awk 'NR % 2 == 0' data

"Justice is such a fine thing that we cannot pay too dearly for it" - Alain-Rene Lesage

Related:

GNU Awk User Guide - awk examples

awk one liners - Eric Pement

awk one liners explained & pt2 - Peteris Krumin (CatOnMat.net)

Patrick Hartigan - How to use awk

`awk', `oawk', and `nawk' - Alternative, older and newer versions of awk

egrep - egrep foo FILES ...is essentially the same as awk '/foo/' FILES ...

expr - Evaluate expressions

eval - Evaluate several commands/arguments

for - Expand words, and execute commands

grep - search file(s) for lines that match a given pattern

m4 - Macro processor

tr - Translate, squeeze, and/or delete characters

Equivalent Windows command: FOR - Conditionally perform a command several times.