How to loop over directories in Linux?

Question

I am writing a script in bash on Linux and need to go through all subdirectory names in a given directory. How can I loop through these directories (and skip regular files)?

For example:
the given directory is /tmp/
it has the following subdirectories: /tmp/A, /tmp/B, /tmp/C

I want to retrieve A, B, C.

Answer 1

If you want to execute multiple commands in a for loop, you can save the result of find with mapfile (bash >= 4) as an variable and go through the array with ${dirlist[@]}. It also works with directories containing spaces.

The find command is based on the answer by Boldewyn. Further information about the find command can be found there.

IFS=""
mapfile -t dirlist < <( find . -maxdepth 1 -mindepth 1 -type d -printf '%f\n' )
for dir in ${dirlist[@]}; do
    echo ">${dir}<"
    # more commands can go here ...
done

Answer 2

find . -mindepth 1 -maxdepth 1 -type d -printf "%P\n"

Answer 3

cd /tmp
find . -maxdepth 1 -mindepth 1 -type d -printf '%f\n'

A short explanation: find finds files (quite obviously)

• . is the current directory, after the cd it's /tmp (IMHO this is more flexible than having /tmp directly in the find command. You have only one place, the cd, to change, if you want more actions to take place in this folder)

• -maxdepth 1 and -mindepth 1 make sure, that find really, only looks in the current dir and doesn't include '.' in the result

• -type d looks only for directories

• -printf '%f\n prints only the found folder's name (plus a newline) for each hit.

E voila!

Answer 4

You can loop through all directories including hidden directrories (beginning with a dot) with:

for file in */ .*/ ; do echo "$file is a directory"; done

note: using the list */ .*/ works in zsh only if there exist at least one hidden directory in the folder. In bash it will show also . and ..

---

Another possibility for bash to include hidden directories would be to use:

shopt -s dotglob;
for file in */ ; do echo "$file is a directory"; done

---

If you want to exclude symlinks:

for file in */ ; do 
  if [[ -d "$file" && ! -L "$file" ]]; then
    echo "$file is a directory"; 
  fi; 
done

---

To output only the trailing directory name (A,B,C as questioned) in each solution use this within the loops:

file="${file%/}"     # strip trailing slash
file="${file##*/}"   # strip path and leading slash
echo "$file is the directoryname without slashes"

Example (this also works with directories which contains spaces):

mkdir /tmp/A /tmp/B /tmp/C "/tmp/ dir with spaces"
for file in /tmp/*/ ; do file="${file%/}"; echo "${file##*/}"; done

Answer 5

find . -type d -maxdepth 1

Answer 6

The technique I use most often is find | xargs. For example, if you want to make every file in this directory and all of its subdirectories world-readable, you can do:

find . -type f -print0 | xargs -0 chmod go+r
find . -type d -print0 | xargs -0 chmod go+rx

The -print0 option terminates with a NULL character instead of a space. The -0 option splits its input the same way. So this is the combination to use on files with spaces.

You can picture this chain of commands as taking every line output by find and sticking it on the end of a chmod command.

If the command you want to run as its argument in the middle instead of on the end, you have to be a bit creative. For instance, I needed to change into every subdirectory and run the command latemk -c. So I used (from Wikipedia):

find . -type d -depth 1 -print0 | \
    xargs -0 sh -c 'for dir; do pushd "$dir" && latexmk -c && popd; done' fnord

This has the effect of for dir $(subdirs); do stuff; done, but is safe for directories with spaces in their names. Also, the separate calls to stuff are made in the same shell, which is why in my command we have to return back to the current directory with popd.