Everybody knows, there is paste command in every *NIX to print two files side by side or join which is obviously used to join text-files by their key-fields. And there are a lot of examples and tutorials over Internet, so the subject is as trivial as cat-ting files together with right command-line options.
Ah, wait… What if we have textual data stored not in files but in two variables as a result, for example, of piping or redirection?
Imagine there’s no heaven two variables:
a="aa qq
bb ww
cc ee"
b="11 44
22 55
33 66"
And we want to see this as the result:
aa qq | 11 44
bb ww | 22 55
cc ee | 33 66
It’s not an issue having Bash and arrays:
#!/usr/bin/env bash
a="aa qq
bb ww
cc ee"
b="11 44
22 55
33 66"
IFS=$'\n' read -d '' -a a_arr <<< "$a"
IFS=$'\n' read -d '' -a b_arr <<< "$b"
for i in ${!a_arr[@]}; do
echo ${a_arr[i]} "|" ${a_arr[i]}
done
The main trick is done with read command which stores lines in arrays, while the rest is just a loop which scans arrays to print lines with the same index.
But life is not always easy and sometimes one could still deal with pure old Bourne shell without any hints on arrays where set command was utilised to create $@ array of $1 to $n elements. Agree, this is not always handy.
So, in the worst case it’s always possible to use a counter variable and an external tool to scan over the strings. For example, awk:
#!/bin/sh
a="aa qq
bb ww
cc ee"
b="11 44
22 55
33 66"
cnt=0
echo "$a" | while read -r ln; do
cnt=`expr $cnt + 1`
printf "$ln | "
printf "$b" | awk -v c="$cnt" 'NR==c {print}'
done
or even like this:
#!/bin/bash
a="aa qq
bb ww
cc ee"
b="11 44
22 55
33 66"
for l in $(seq 1 `wc -l <<< "$a"`); do
awk -v l="$l" 'BEGIN {ORS=" | "} NR==l {print}' <<< "$a"
awk -v l="$l" 'NR==l {print}' <<< "$b"
done
Keeping in mind external tools and languages, there are much more possibilities to do the task, but lets stop on this for a while 🙂
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