Variable scope and debugging

rkrishnan73 · #1 (**permalink**) 04-02-04, 09:59

Hi

How is a variable's scope handled in bash? Here's the code skeleton.

var=0
while read oneLine
do
# do some mathematics with $var
# and the value read from the file

echo $var # displays variable value correctly for each stage

done < $inputFile

echo "Loop done.. $var" # displays accumulated variable value as 0

When I write set -a var it works, but I'm unable to debug the script any more by specifying set -x. Can we not do both at the same time?

Thanks in advance.

- Ram.

aigles · #2 (**permalink**) 04-02-04, 10:39

I am using cgywin bash and i don't have this problem :

Code:

Var=0
echo "Before loop Pid:$$ Var:$Var"
while read oneline
do
   ((Var += 1))
    echo "   Inside loop Pid:$$ Var:$Var"
done < a.a
echo "After loop Pid:$$ Var:$Var"

the result is :

Quote:

Before loop Pid:429381 Var:0
Inside loop Pid:429381 Var:1
Inside loop Pid:429381 Var:2
Inside loop Pid:429381 Var:3
Inside loop Pid:429381 Var:4
Inside loop Pid:429381 Var:5
Inside loop Pid:429381 Var:6
After loop Pid:429381 Var:6

Some version of shell creates a subprocess to execute the statements into the loop, in that case the modifications of the environment are lost when exiting the loop.
Try my script and verify that the Pid is the pid is the same outside and inside the loop.

You can also try to export your variable.

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