CODEWITHSUNDEEP
regexbashawk
ton
ton

Reputation: 4597

awk lines not match

Using AWK, I need to avoid print lines with a specific word in a specific field... Before someone call it's a duplicate, I did search, and found this: Match string not containg a certain phrase, but I think it's other context, because here I need match in a specific column.

Given the data:

ABC      ABC
DEF      AAA
GHI      ABC

I want to filter to print full lines only with text not containing ABC in fist field(lines 2 and 3).

As a first try, I tried (?!...) and expected to work this way to return DEF and GHI:

echo -e "ABC\tABC\nDEF\tAAA\nGHI\tABC" | awk '$1 ~ /(?!ABC)/ {print}'

but return nothing.

Second try... using not before the expression !/.../ :

~$ echo -e "ABC\tABC\nDEF\tAAA\nGHI\tABC" | awk '$1 ~ !/ABC/ {print}'

Return nothing too.

I don't understand why...

So another shot fails (as expected this time):

~$ echo -e "ABC\tABC\nDEF\tAAA\nGHI\tABC" | awk '!/ABC/ {print}'
DEF     AAA

As expected this time, the second field was filtered too. So, it seems it work only to $0.

Then I did my homework and got it working this way:

~$ echo -e "ABC\tABC\nDEF\tAAA\nGHI\tABC" | awk '{FL=$0;$0=$1}; !/ABC/ {print FL}; { $0=FL }'
DEF     AAA
GHI     ABC

Anyway, this looks a workaround for me, and I have a bad feeling that I'm not doing in the right way.

Someone know a better way, or at least explain why the first and second tries do not worked ?

Upvotes: 1

Views: 99

Answers (2)

Jotne
Jotne

Reputation: 41460

This awk should do:

awk '!/^ABC/' file
DEF      AAA
GHI      ABC

It will print lines not (!) starting (^) with ABC

Upvotes: 0

hek2mgl
hek2mgl

Reputation: 158100

You can use the following idiom:

awk '$1 !~ /ABC/' file

If the first field does not contain ABC the line gets printed. (The matches not operator is !~). Note that the command contains a condition only and no print action. This can work since the default action in awk is print and therefore does not need to get specified explicitly.

Upvotes: 2

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