Create a subdirectory for all directories in folder

Question

Suppose I have some directory, which contain a number of subdirectories, and in each of those subdirectories I want to create a directory with the same name:

./dir-1
./dir-2
...
./dir-n

I want to do mkdir */new-dir

but this throws an error. What's the best way of going about this?

Answer 1

for dir in $(ls); do
  mkdir "$dir/new-dir"
done

Answer 2

find . -type d | xargs -I "{x}" mkdir "{x}"/new-dir

If you want to reduce it to the first level of directories use

find . -maxdepth 1 -type d | xargs -I "{x}" mkdir "{x}"/new-dir

Answer 3

Amazing that this question never obtained a sane answer:

shopt -s nullglob
for i in */; do
    mkdir -- "${i}newdir"
done

• This is 100% safe regarding funny symbols in filenames (spaces, wildcards, etc.).
• The shopt -s nullglob so that the glob expands to nothing if there are no matches.
• The -- in mkdir to mark the end of options (if there's a directory with a name starting with a hyphen, doesn't confuse mkdir trying to interpret it as an option).

This silently ignores the hidden directories. If you need to perform this operation on hidden directories, just replace the line shopt -s nullglob by the following:

shopt -s nullglob dotglob

The dotglob so that the globs also consider hidden files/directories.

If you want only one invocation of mkdir:

shopt -s nullglob
dirs=( */ )
mkdir -- "${dirs[@]/%/newdir}"