Question

I have 2 different scripts doing basically the same: counting the subdirectories in the current directory:

c=0

ls -l | grep "^d" | while read zeile
do
    c=`expr $c + 1`
    echo $c
done

echo "Subdirs: $c"

and

c=0

while read zeile
do
    c=`expr $c + 1`
    echo $c
done < <(ls -l | grep "^d")

echo "Subdirs: $c"

My Problem is, that in the first version, “c” seems to lose it’s value after the while-loop has finished.

The outputs

1)

1
2
3
Subdirs: 0

2)

1
2
3
Subdirs: 3

Can anyone of you explain to me, why this is happening?

Thanks in advance
Alex

Answer 1

In the first case, the assignment to c happens after the |, i.e. in a subshell. You cannot change a variable in a parent shell from a subshell.
BTW, why do not you use let c++ instead of backquotes and expr?