Variable Erased When The Loop Is Done

I wrote this simple script :

#!/bin/bash
cnf=X
ls *.cnf* > toto.txt
N=0
cat toto.txt | while read LINE ; do
N=$((N+1))
exten=${LINE##*.}
case $exten in
cnf1) cnf=Y ;;
cnf2) ..... ;;
esac
echo "$cnf" ; This displays Y when the condition is met
done
echo "$cnf" : This always display X whatever happened in the loop

I tried to export, declare ..... still the same.
I am not familiar with linux but still feel able to handle this kind of stuff at the condition I can get the value after the loop...

Its maybe a very beginner question but I did nt get any answer in my readings if anybody can help...

I can't reproduce your problem but your script is unnecessarily complex.

You can just do:

#!/bin/bash
cnf=X
N=0
for LINE in *.cnf* ; do
N=$((N+1))
exten=${LINE##*.}
case $exten in
cnf1) cnf=Y ;;
cnf2) ..... ;;
esac
echo "$cnf"
done
echo "$cnf"
[/b]

I can't reproduce your problem but your script is unnecessarily complex.

You can just do:
[/b]

I tried your way and it works like a charm. A very big thanks.

I'll try when i will be a bit less pressured to put my old code in a lab to understand this weird behavior even if its a weird code

Actually I think I know what your problem is. When you do

cat toto.txt | while read LINE
do
done

you are running the while in a different shell instance because of the piping and redirection, so the variable there will belong to that shell not to the outer one.

But this should work:

for LINE in $(cat toto.txt)
do
done

or better still, what I showed you, forget about the intermediate file toto.txt.

Ironically I hit this same issue yesterday using "while" instead of "for"

I actually only need the final answer from the entire thing, so what I did was pipe all to "tail -1" and then run the whole lot in a seperate shell with the output going into a variable, a very messy way of doing it, but it worked for me, I might try some of these other ways though.


as you're using Bash, there is a work-around (unfortunately all my scripts are written in Korn Shell, which doesn't have this work-around) this is how I would do this in Bash:

#!/bin/bash

cnf=X
ls *.cnf* > toto.txt
N=0
while read LINE; do
N=$((N+1))
exten=${LINE##*.}
case $exten in
cnf1) cnf=Y;;
cnf2) .....;;
esac
echo "$cnf"; This displays Y when the condition is met
done < <(cat toto.txt)
echo "$cnf" : This always display X whatever happened in the loop

the difference here is instead of piping your cat to the while loop, you have your loop, and the "done" line gets the condition

This is Bash's work-around for this problem

of course, everyone has their own ways of doing these scripts, this is generally mine when I'm using bash.

Jason.