Arithmetic operation in variable

Shell Programming and Scripting
1

Hi,

Here is the script i try to perform arithmetic operation in two variables .

git branch -r | while read brname ; do
REV_COMMITS=`git rev-list --count $brname`
echo "$brname has $REV_COMMITS"
(( TOTAL = TOTAL + REV_COMMITS ))
echo "in loop" $TOTAL
done
echo "total is " $TOTAL

Output:

In side the loop, i get correct value of variable TOTAL.
How to get correct TOTAL outside while loop ?

2

This question pops up an awful lot.

When you run shell commands in a pipe, they exist inside a different shell. This shell sums up the value perfectly and quits - leaving you in your original shell where the value was never changed.

Which end of the pipe is 'your' shell can vary from shell to shell. In KSH, you'd have gotten the total; I suspect you're running bash.

There's a few ways to deal with this and make it work in both.

Stuffing the entire program into the subshell with ( ) grouping braces:

git branch -r | (
        while read something
        do
                ...
        done 

        echo "total is $total"
)

Here-doc:

while read something
do
...
done <<EOF
$(git branch -r)
EOF

You could also use a temp file.

1 Like
3

Please don't ask technical questions in private messages.

Subshells

4

You could also have the loop as:-

while read something
do
   whatever
done < <(git branch -r)

Note that space between the two < characters.

I hope that this helps,
Robin