AWK: shortened if-then-else with regex

Question

The following AWK format:

/REGEX/ {Action}

Will execute Action if the current line matches REGEX.

Is there a way to add an else clause, which will be executed if the current line does not matches the regex, without using if-then-else explicitly, something like:

/REGEX/ {Action-if-matches} {Action-if-does-not-match}

Zsolt Botykai · Accepted Answer · 2013-10-30T06:23:44.883

19

Not so short:

/REGEX/ {Action-if-matches} 
! /REGEX/ {Action-if-does-not-match}

But (g)awk supports the ternary operator too:

{ /REGEX/  ? matching=1 : matching = 0 ; if ( matching ==1 ) { matching_action } else { notmatching_action } }

UPDATE:

According to the great Glenn Jackman you can assign variables on the match like:

m = /REGEX/ { matching-action } !m { NOT-matching-action }

edited Oct 30 '13 at 06:23

answered Jan 23 '13 at 11:36

Zsolt Botykai

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1

Is that ternary supposed to be *inside* the braces? If so, does it actually do what OP asked for? – kojiro Jan 23 '13 at 12:49
You were right, you cant perform "actions" other than assigning values with the ternary checking. – Zsolt Botykai Jan 23 '13 at 13:09
4

You could assign the boolean value of the match: `m = /regex/ {matching action} !m {non-matching action}` – glenn jackman Oct 29 '13 at 17:38

score 16 · Answer 2 · answered Jan 23 '13 at 14:30

16

There's also next:

/REGEX/ {
    Action
    next # skip to the next line
}
{ will only get here if the current line does *not* match /REGEX/ }

answered Jan 23 '13 at 14:30

glenn jackman

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score 1 · Answer 3 · answered Jan 23 '13 at 12:45

You can do a "trick". As you know AWK tries to match the input to each regex in order, to execute its block.

This code executes the second block if $1 is "1", else it executes the third block:

awk '{used = 0} $1 == 1 {print $1" is 1 !!"; used = 1;} used == 0 {print $1" is not 1 !!";}'

If the input is:

1
2

It prints:

1 is 1 !!
2 is not 1 !!

AWK: shortened if-then-else with regex

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