Use values in a column to separate strings in another column in bash

Question

I am trying to separate a column of strings using the values from another column, maybe an example will be easier for you to understand.

The input is a table, with strings in column 2 separated with a comma ,.
The third column is the field number that should be outputted, with , as the delimited in the second column.

Ben mango,apple 1
Mary    apple,orange,grape  2
Sam apple,melon,*   3
Peter   melon   1

The output should look like this, where records that correspond to an asterisk should not be outputted (the Sam row is not outputted):

Ben mango
Mary    orange
Peter   melon

I am able to generate the desired output using a for loop, but I think it is quite cumbersome:

IFS=$'\n'
for i in $(cat input.txt)
do
    F=`echo $i | cut -f3`
    paste <(echo $i | cut -f1) <(echo $i | cut -f2 | cut -d "," -f$F) | grep -v "\*"
done

Is there any one-liner to do it maybe using sed or awk? Thanks in advance.

Shawn · Accepted Answer · 2021-08-12 07:29:54Z

1

The key to doing it in awk is the split() function, which populates an array based on a regular expression that matches the delimiters to split a string on:

$ awk '{ split($2, fruits, /,/); if (fruits[$3] != "*") print $1, fruits[$3] }' input.txt
Ben mango
Mary orange
Peter melon

answered Aug 12, 2021 at 7:29

Shawn

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