Nested functions in for loop not working

Question

Nested functions in for loop seems to be not working as expected. The loop breaks after iterating once

# copy files
copyFiles () {
   for (( i=0; i<${#filetype[@]}; ++i )); do
     //some code goes here
   done
}

# copy common components
copyComponents () {
  copyFiles $1
}

for (( i=0; i<3; ++i )); do
  echo $i //iterates only once.. expectation is thrice
  case $1 in
    components)
       copyComponents $module;;
    *)
       echo "unknown type"
   esac
done

I am not sure what I am doing wrong but for loop exits after iterating once.

chepner · Accepted Answer · 2016-04-12 17:40:50Z

3

The problem is that all variables in shell are global unless declared otherwise. Here's a simpler example that demonstrates this:

func () {
    for ((i=0; i<10; ++i)); do
        echo "func: $i"
    done
}

for ((i=0; i<5; ++i)); do
    echo "Loop: $i"
    func
done

echo "$i"

If you run the, you'll see that after func is executed the first time, the value of the global variable i is 11, which causes the outer loop to exit. To fix this in bash, you can ensure that the loop counter in your function stays local.

copyFiles () {
    local i
    for (( i=0; i<${#filetype[@]}; ++i )); do
        # some code goes here
    done
}

answered Apr 12, 2016 at 17:40

chepner

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