extract information from a file with loop

Question

I need help :) I have a file like this:

AA BC FG

RF TT GH

DD FF HH

(a few number of rows and three columns) and I want to put the letters of each column in a variable step by step in order to give them as input in another script. So I would like to obtain:

for the 1° loop:

var1 = AA
var2 = BC
var3 = FG

for the 2° loop:

var1 = RF
var2 = TT
var3 = GH

for the 3° loop:

var1 = DD
var2 = FF
var3 = HH

Answer 1

If you file has exactly 3 whitespace-separated items on each line (no blank lines for example) then you should be able to use a simple while ... read loop:

while read -r var1 var2 var3; do
  ./otherscript "$var1" "$var2" "$var3"
done < "file"

If there are blank lines, then you should probably read complete lines and only parse the non-empty ones e.g.

while IFS= read -r line; do
  if [[ -n "$line" ]]; then 
    read -r var1 var2 var3 <<< "$line"
    ./otherscript "$var1" "$var2" "$var3"
  fi
done < "file"

Answer 2

Considering that your input file only provides arguments to script, the xargs is a reasonable choice in this situation. Lets take this script as example:

#!/bin/bash
echo "This is a test"
echo "var1 is $1 " "var 2 is $2 " "var 3 is $3"

We can use xargs with -L1 for taking 1 line in file as arguments, and --arg-file to specify the file containing those arguments. Thus:

$ xargs -L 1 -r --arg-file=input.txt ./somescript.sh 
This is a test
var1 is AA  var 2 is BC  var 3 is FG
This is a test
var1 is RF  var 2 is TT  var 3 is GH
This is a test
var1 is DD  var 2 is FF  var 3 is HH

Notice the -r option, which prevents xargs from running the script on blank lines, which are contained in your input file example.