[SOLVED] Is my version of awk working?

cvbngrocks · 11-14-2018, 05:48 AM

Salutations everyone

I am trying to get awk to return lines with 3 exact matches of string.

Quote:

i=fox
j=fox
k=fox

awk -v str1="$i" -v str2="$j" -v str3="$k" '$0~str1 && $0~str2 && $0~str3' file

the fox kill the other fox and the fox felt bad
the fox is dead

Why is awk returning the second line with one fox string? Is my syntax wrong or is something missing? How can I make awk return the first line only? Thanks

syg00 · 11-14-2018, 06:04 AM

Your version of awk is working fine. In almost all occasions when you think awk (or any other language/interpreter) is failing, think again - it will be a user error.
As in this case.

Read your logic more carefully - then try with different variable assignments and see what happens. Learning is trying things.

berndbausch · 11-14-2018, 08:02 AM

i hope svg00 forgives me, but here is a clue: You check three times whether the line contains the string fox. The result is the same as checking once, twice or 100 times.

cvbngrocks · 11-14-2018, 08:51 PM

Quote:

Originally Posted by syg00

Your version of awk is working fine. In almost all occasions when you think awk (or any other language/interpreter) is failing, think again - it will be a user error.
As in this case.

Read your logic more carefully - then try with different variable assignments and see what happens. Learning is trying things.

I got the syntax right as I found examples online.

Thanks syg00 for the replay

Quote:

Originally Posted by berndbausch

i hope svg00 forgives me, but here is a clue: You check three times whether the line contains the string fox. The result is the same as checking once, twice or 100 times.

I didn't know hat.

I thought that using the explicit && would mean all three conditions must be true. It did work for the first line . LOL

Thanks berndbausch for the reply

MadeInGermany · 11-15-2018, 12:38 PM

The && is correct, but you need 3 different checks:
if {a word matches str1} && {a different word matches str2} && {yet a different word matches str3}

It can be implemented by 3 nested loops, where the inner loop searches right from the current word in the outer loop...
Or by a regular expression. That is a bit tricky; I found the following solution (for Posix-compatible awk)

Code:

awk -v str1="$i" -v str2="$j" -v str3="$k" 'BEGIN { s="[[:space:]]"; gap=(s "(.*" s ")?") } (" " $0 " ") ~ (s str1 gap str2 gap str3 s)' file

In the long RE string the str3 is right from the str2 that is right from the str1.

berndbausch · 11-15-2018, 03:39 PM

Quote:

Originally Posted by cvbngrocks

I thought that using the explicit && would mean all three conditions must be true. It did work for the first line

It does mean that all three conditions must be true. But all three conditions are identical in your case. A && A is the same as A or A && A && A.

syg00 · 11-15-2018, 05:34 PM

Quote:

Originally Posted by cvbngrocks

I got the syntax right as I found examples online.

I said check you logic, not your syntax.
As explained a couple of times by berndbausch.

Change one of the vars to "fx" and see what happens.

cvbngrocks · 11-15-2018, 10:08 PM

Code:

i=trump; j=fox; k=toupee;awk -v str1="$i" -v str2="$j" -v str3="$k" '$0~str1 && $0~str2 && $0~str3' file 
trump asked the fox if he can use the fox's fur as a toupee

You guys are right. I used three different items and awk return the line with those three matches.

I got it now

MadeInGermany · 11-16-2018, 01:49 AM

The correct input matters.

cvbngrocks · 11-16-2018, 02:23 AM

Quote:

Originally Posted by MadeInGermany

The correct input matters.

Thanks

BTW, the next line in the file was:

The fox said, "OK! As long as you don't called it fake."