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Awk: split and gensub query


 
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# 1  
Awk: split and gensub query

Hi All,

Thanks for answering my previous question. Could you please explain the highlighted code?

Code:
awk -v pos='9 27 39 54 59 64 71 78 83 103 108' 'BEGIN{split(pos,var)} {for (i in var) $0=gensub(/./,"|",var[i])} 1' test.txt | head

I understood that the split function splits the pos string into an array but I am confused on the usage of gensub function, especially var[i]. It wold be helpful if there is any tool which I use to visualize the steps.

Thanks,
Mc

Last edited by mrcool4; 08-13-2019 at 05:09 AM.. Reason: Added more info
# 2  
You are right - the pos variable is split into the var array. Then, in all input lines ($0), gensub (a specific gawk function) replaces the characters (no matter what they are!) at the positions in var by the pipe symbol, as said in man gawk:

Quote:
gensub(regexp, replacement, how [, target])
Search the target string target for matches of the regular expression regexp. If how is a string beginning with ‘g' or ‘G' (short for “global”¯), then replace all matches of regexp with replacement. Otherwise, treat how as a number indicating which match of regexp to replace. Treat numeric values less than one as if they were one. If no target is supplied, use $0. Return the modified string as the result of the function. The original target string is not changed.
This User Gave Thanks to RudiC For This Post:
# 3  
Thanks Rudic. Got it. I have been trying to understand by simplifying the function and finally understood by trying with a few examples.

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