How to loop over directories in Linux? - 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

All answers so far use find, so here's one with just the shell. No need for external tools in your case:
for dir in /tmp/*/ # list directories in the form "/tmp/dirname/"
do
dir=${dir%*/} # remove the trailing "/"
echo "${dir##*/}" # print everything after the final "/"
done

Answer 2

cd /tmp
find . -maxdepth 1 -mindepth 1 -type d -printf '%f\n'
A short explanation:
find finds files (quite obviously)
. is the current directory, which after the cd is /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 only looks in the current directory and doesn't include . itself 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.
Et voilà!

Answer 3

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 4

Works with directories which contains spaces
Inspired by Sorpigal
while IFS= read -d $'\0' -r file ; do
echo $file; ls $file ;
done < <(find /path/to/dir/ -mindepth 1 -maxdepth 1 -type d -print0)
Original post (Does not work with spaces)
Inspired by Boldewyn: Example of loop with find command.
for D in $(find /path/to/dir/ -mindepth 1 -maxdepth 1 -type d) ; do
echo $D ;
done

Answer 5

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

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.

Answer 7

a minimal bash loop you can build off of (based off ghostdog74 answer)
for dir in directory/*
do
echo ${dir}
done
to zip a whole bunch of files by directory
for dir in directory/*
do
zip -r ${dir##*/} ${dir}
done

Answer 8

If you want to execute multiple commands in a for loop, you can save the result of find with mapfile (bash >= 4) as a 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 9

TL;DR:
(cd /tmp; for d in */; do echo "${d%/}"; done)
Explanation.
There's no need to use external programs. What you need is a shell globbing pattern. To avoid the need of removing /tmp afterward, I'm running it in a subshell, which may or not be suitable for your purposes.
Shell globbing patterns in a nutshell:
* Match any non-empty string any number of times.
? Match exactly one character.
[...] Matches with a character from between the brackets. You can also specify ranges ([a-z], [A-F0-9], etc.) or classes ([:digit:], [:alpha:], etc.).
[^...] Match one of the characters not between the braces.
* If no file names match the pattern, the shell will return the pattern unchanged. Any character or string that is not one of the above represents itself.
Consequently, the pattern */ will match any file name that ends with a /. A trailing / in a file name unambiguously identifies a directory.
The last bit is removing the trailing slash, which is achieved with the variable substitution ${var%PATTERN}, which removes the shortest matching pattern from the end of the string contained in var, and where PATTERN is any valid globbing pattern. So we write ${d%/}, meaning we want to remove the trailing slash from the string represented by d.

Answer 10

find . -type d -maxdepth 1

Answer 11

In short, put the results of find into an array and iterate the array and do what you want. Not the quickest but more organized thinking.
#!/bin/bash
cd /tmp
declare -a results=(`find -type d`)
#Iterate the results
for path in ${results[#]}
do
echo "Your path is $path"
#Do something with the path..
if [[ $path =~ "/A" ]]; then
echo $path | awk -F / '{print $NF}'
#prints A
elif [[ $path =~ "/B" ]]; then
echo $path | awk -F / '{print $NF}'
#Prints B
elif [[ $path =~ "/C" ]]; then
echo $path | awk -F / '{print $NF}'
#Prints C
fi
done
This can be reduced to find -type d | grep "/A" | awk -F / '{print $NF}' prints A
find -type d | grep "/B" | awk -F / '{print $NF}' prints B
find -type d | grep "/C" | awk -F / '{print $NF}' prints C