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




(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
  • You should post generic programming questions in StackOverflow. – negusp Nov 8 '16 at 16:25
  • ops, I am sorry :( – pingu Nov 8 '16 at 16:33
  • Hmm I think this is possibly on topic, seems loosely like a text processing question @PatrickNegus – Zanna Nov 8 '16 at 17:18
  • 1
    @Zanna while that may be true, I don't know what language OP want to use; even more, its easier if collective programming questions/answers are posted in their correct sub-Exchange as it makes it easier for other people with similar issues to get answers. – negusp Nov 8 '16 at 17:35
  • 1
    while read -r var1 var2 var3; do <something with them>; done < file – steeldriver Nov 8 '16 at 17:40

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"
done < "file"
  • read -r var1 ... on a blank line would leave $var1 empty which might be a more elegant way to test for blank lines. – David Foerster Nov 9 '16 at 0:41

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:

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.

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