Question

I’m pretty new to bash scripting and I’m obviously missing some fairly basic understanding as I can’t work out why this script isn’t doing as I’d expect. I’ve made a simple example reproducing the problem, it is supposed to make 3 folders, with 3 folders inside, then touch a file test inside of each.

Here’s the script:

#!/bin/sh
DIR_LEVEL_1=("1" "2" "3")
for DIR_1 in ${DIR_LEVEL_1[@]}; do
  mkdir $DIR_1
  DIR_LEVEL_2=("$DIR_1/a" "$DIR_1/b" "$DIR_1/c")
  echo $DIR_LEVEL_2
  for DIR_2 in ${DIR_LEVEL2[@]}; do
    mkdir $DIR_2
    touch "$DIR_2/test"
  done
done

The problem I was having was the it wasn’t entering the second for loop, I put in that echo and it looks like the second array isn’t being created properly as the output of the script is:

1/a
2/a
3/a

which is just the first element of the array.

running with -xv flag I get this, which shows it’s taking no notice of that nested for loop (I guess because the array didn’t get created as I wanted?)

#!/bin/sh
DIR_LEVEL_1=("1" "2" "3")
+ DIR_LEVEL_1=("1" "2" "3")
for DIR_1 in ${DIR_LEVEL_1[@]}; do
  mkdir $DIR_1
  DIR_LEVEL_2=("$DIR_1/a" "$DIR_1/b" "$DIR_1/c")
  echo $DIR_LEVEL_2
  for DIR_2 in ${DIR_LEVEL2[@]}; do
    mkdir $DIR_2
    touch "$DIR_2/test"
  done
done
+ for DIR_1 in '${DIR_LEVEL_1[@]}'
+ mkdir 1
+ DIR_LEVEL_2=("$DIR_1/a" "$DIR_1/b" "$DIR_1/c")
+ echo 1/a
1/a
+ for DIR_1 in '${DIR_LEVEL_1[@]}'
+ mkdir 2
+ DIR_LEVEL_2=("$DIR_1/a" "$DIR_1/b" "$DIR_1/c")
+ echo 2/a
2/a
+ for DIR_1 in '${DIR_LEVEL_1[@]}'
+ mkdir 3
+ DIR_LEVEL_2=("$DIR_1/a" "$DIR_1/b" "$DIR_1/c")
+ echo 3/a
3/a

So it only creates the first level of folders

Answer 1

Well, the real issue with your script is that you create DIR_LEVEL_2, but you iterate over DIR_LEVEL2. (Note the underscore difference). However, you also neglect to quote "${array[@]}", which means it will not wordsplit properly. All that aside, might I suggest you use brace expansion to make this entire thing a better experience?

#!/bin/bash

dirs=( {1,2,3}/{a,b,c} )
mkdir -p "${dirs[@]}"
for d in "${dirs[@]}"; do
    touch "$d/test"
done

Edit/postscript: I notice your script above uses #!/bin/sh, but you’ve tagged this post bash. They are not the same thing. Unless you’re certain you want to trade the greater featureset of bash for the greater portability of sh, use #!/bin/bash.