bash: piped loop in same shell

Vit77 · 04-30-2009, 02:38 AM

Hi,

I'm trying to update variable's value in a piped loop:

Code:

a=0
txt='a\nb\nc'
echo -e "$txt" | while read line
do
  # do smth with $line ...
  a=$((a+1))
  echo $a
done

echo "Final: $a"

Result:

Code:

1
2
3
Final: 0

So, this while-loop was executed in a new shell, and original variable $a was not changed.

Is it possible to use such piped loop within the same shell, or how to keep the changed value outside?

Thanks!

colucix · 04-30-2009, 02:46 AM

Use process substitution instead of the pipe:

Code:

#!/bin/bash
a=0
txt='a\nb\nc'
while read line
do
  # do smth with $line ...
  a=$((a+1))
  echo $a
done < <(echo -e "$txt")

echo "Final: $a"

this does not run the loop in a subshell and keeps the last updated value of the variable.

Vit77 · 04-30-2009, 02:50 AM

It works great! Thank you!