awk print column $3 if $2==a specific value?

问题:

I'm learning awk from The awk programming language and being bothered by this example.

If i want to print $3 if $2 is equal to a value(e.g.'1'), and I was using this command which works fine:

awk '$2==1 {print $3}' <infile> | more

But when I substitute 1 by another searching criteria, for example 'findtext' and this command doesn't work.

awk '$1== findtext {print $3}' <infile> | more

This returns nothing output and I'm sure what I put in 'findtext' was exist in that place. Is there anything wrong with my syntax?

I tried this but it doesn't work:

awk '$1== "findtext" {print $3}' <infile> | more

But when I do

grep findtext <infile>  ## This does give me output

The findtext is exist in the $1 as I double checked.

Here's my test file named 'test' for example, it has 9 lines and and 8 fields and space separated:

1 11 0.959660297 0 0.021231423 -0.0073 -0.0031 MhZisp
2 14 0.180467091 0.800424628 0 0.0566 0.0103 ClNonZ
3 19 0.98089172 0 0 -0.0158 0.0124 MhNonZ
4 15 0.704883227 0.265392781 0.010615711 -0.0087 -0.0092 MhZisp
5 22 0.010615711 0.959660297 0.010615711 0.0476 0.0061 ClNonZ
6 23 0.715498938 0 0.265392781 -0.0013 -0.0309 Unkn
7 26 0.927813163 0 0.053078556 -0.0051 -0.0636 MhZisp
8 44 0.55626327 0.222929936 0.201698514 0.0053 -0.0438 MhZisp
9 31 0.492569002 0.350318471 0.138004246 0.0485 0.0088 ClNonZ

Here's what I did and the output:

$awk '$8 == "ClNonZ" {print $3}' test 

$ grep ClNonZ test 
2 14 0.180467091 0.800424628 0 0.0566 0.0103 ClNonZ
5 22 0.010615711 0.959660297 0.010615711 0.0476 0.0061 ClNonZ
9 31 0.492569002 0.350318471 0.138004246 0.0485 0.0088 ClNonZ

I expect to see this which is the $3 that has "ClNonZ" in their $8.

0.180467091 
0.010615711 
0.492569002

Don't know why the awk command didn't return anything. any thoughts?

回答1:

If you're looking for a particular string, put quotes around it:

awk '$1 == "findtext" {print $3}'

Otherwise, awk will assume it's a variable name.

回答2:

This method uses regexp, it should work:

awk '$2 ~ /findtext/ {print $3}' <infile>

回答3:

Depending on the AWK implementation are you using == is ok or not.

Have you tried ~?. For example, if you want $1 to be "hello":

awk '$1 ~ /^hello$/{ print $3; }' <infile>

^ means $1 start, and $ is $1 end.

回答4:

My awk version is 3.1.5.

Yes, the input file is space separated, no tabs.

According to arutaku's answer, here's what I tried that worked:

awk '$8 ~ "ClNonZ"{ print $3; }' test  
0.180467091
0.010615711
0.492569002


$ awk '$8 ~ "ClNonZ" { print $3}' test  
0.180467091
0.010615711
0.492569002

What didn't work(I don't know why and maybe due to my awk version:),

$awk '$8 ~ "^ClNonZ$"{ print $3; }' test
$awk '$8 == "ClNonZ" { print $3 }' test

Thank you all for your answers, comments and help!

回答5:

This is more readable for me

awk '{if ($2 ~ /findtext/) print $3}' <infile>

回答6:

please try this

echo $VAR | grep ClNonZ | awk '{print $3}';

or

echo cat filename | grep ClNonZ | awk '{print $3}';