2 while loop to read contents of a file

Question

I have 2 file. Let's say file1 and file2. I want to read the file1 together with the file2 so it will give me an output into one single line.

eg. file1 = contents "123.45.67.89" file2 = contents "hostname.cco"

output: 123.45.67.89 hostname.cco

Im runninng nested loop but seems I can not accoumplish what I want to do.

Answer 1

It's actually quite simple, but it does require reading from more than one file descriptor. Essentially, you set up a read loop, as normal, and redirect a file to fd3 and a second file on stdin , you can then read independent lines from each file on each iteration of the loop. (eg read line1 from file1, line1 from file2, and so on). You can use:

#!/bin/bash

while read -r -u 3 linea; do               ## reads linea from file1
    read -r lineb;                         ## reads lineb from file2
    printf "%s %s\n" "$linea" "$lineb"     ## outputs combined lines
done 3<"$1" <"$2"  ## notice first file on fd3 and 2nd on stdin

exit 0

Example Use/Output

Then using your file content for file1 and file2 , you would get the following output:

$ bash read2fd.sh file1 file2
123.45.67.89 hostname.cco

If that is not what you intended, please let me know and I'm happy to help further.