Question

I know awk has IGNORECASE to make the operation case insensitive. But I am not able to figure out how to use it in a for loop.
For example: Consider this awk script:

{
    for (i = 1; i <= NF; i++)
        counter[$i]++
}

Here I know I can use tolower, but what if I want to do it with IGNORECASE = 1, so that it ignores case while counting.

Answer 1

tolower seems the way to go. Look here for further info:

“In general, you cannot use IGNORECASE to make certain rules case-insensitive and other rules case-sensitive, because there is no straightforward way to set IGNORECASE just for the pattern of a particular rule.17 To do this, use either bracket expressions or tolower(). However, one thing you can do with IGNORECASE only is dynamically turn case-sensitivity on or off for all the rules at once.”

from: The GNU Awk User’s Guide

EDIT:

You should think about a better specification of your problem. Try this:

#Input: hello Hello HELLO World 
#Output: hello 3 World 1 

{for (i=1;i<=NF;i++){
    a=tolower($i) 
    count[a]=$i","count[a]
    }
}

END{for (i in count){
    split(count[i],res,",")
    l=length(res) - 1 
    if (l==1){
        print res[1],1 
    } else {
        print tolower(res[1]),l}
    }
}

HTH Chris