I'm attempting to write a script that will be run in a given directory with many single level sub directories. The script will cd into each of the sub directories, execute a command on the files in the directory, and cd out to continue onto the next directory. What is the best way to do this?
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5 Answers
for d in ./*/ ; do (cd "$d" && somecommand); done
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25So since the answerer has omitted any sort of explanation, I'll attempt one.
for d in ./*/starts a loop that stores every item in./*/(a list of files/folders, in this case) in a variable$d.do (cd "$d" && somecommand);starts the body of the loop. Inside the body, it starts a subshell and runs thecdandsomecommandcommands. Since it is a child shell, the parent shell (the shell from which you're running this command) retains its CWD and other environment variables.donesimply closes the loop body.Qix - MONICA WAS MISTREATED– Qix - MONICA WAS MISTREATED2014-12-06 03:25:05 +00:00Commented Dec 6, 2014 at 3:25 -
1this methodworks for sub directories of directories:
for d in ./*/ ; do (cd "$d" && ls); done,will not work. but,for d in ./*/ ; do (cd "$d" && for d in ./*/ ; do (cd "$d" && ls); done ); donewill work. -using ls as the command in this example.Michael Dimmitt– Michael Dimmitt2016-09-06 13:06:08 +00:00Commented Sep 6, 2016 at 13:06 -
-bash: cd: ./*/: No such file or directorystarikcetin– starikcetin2019-10-26 12:56:43 +00:00Commented Oct 26, 2019 at 12:56 -
if you need nested level, Ref: superuser.com/a/1132088/553982dkb– dkb2019-12-11 05:03:16 +00:00Commented Dec 11, 2019 at 5:03
The best way is to not use cd at all:
find some/dir -type f -execdir somecommand {} \;
execdir is like exec, but the working directory is different:
-execdir command {} [;|+]
Like -exec, but the specified command is run from the
subdirectory containing the matched file, which is not normally
the directory in which you started find. This a much more
secure method for invoking commands, as it avoids race
conditions during resolution of the paths to the matched files.
It is not POSIX.
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Does this work with aliases? I have one to download certain files but it isn't recognizing it when I type in find */.link -type f -execdir md $(cat .link) {} \;Something Jones– Something Jones2014-12-05 15:51:57 +00:00Commented Dec 5, 2014 at 15:51
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@SomethingJones no,
findexecutes those commands, so it wouldn't be aware of aliases. What ismdand is the.linka directory?muru– muru2014-12-05 15:52:58 +00:00Commented Dec 5, 2014 at 15:52 -
.link is a text file that has the URL it needs to download. md is an alias to wget with a bunch of flags set. Is there a way to make it aware of aliases?Something Jones– Something Jones2014-12-05 16:15:03 +00:00Commented Dec 5, 2014 at 16:15
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@SomethingJones For your particular use-case, in
bash:find . -type f -iname '*.link' -execdir ${BASH_ALIASES[md]} -i {} \;You don't need to docatwithwget, which has an-iflag for reading in an URL from a file. Also this is somewhat different from your original question (since you seem to be interested in only files named.linkand not any other files which may be present).muru– muru2014-12-05 16:20:16 +00:00Commented Dec 5, 2014 at 16:20 -
Do you know how to do that with zsh? I tried what you gave me and am getting a "Bad substitution" error. Also, how would I be able to extract the content of the .link file? I know I don't need it in this case but I imagine I will soon.Something Jones– Something Jones2014-12-05 21:13:33 +00:00Commented Dec 5, 2014 at 21:13
for D in ./*; do
if [ -d "$D" ]; then
cd "$D"
run_something
cd ..
fi
done
cd -P .
for dir in ./*/
do cd -P "$dir" ||continue
printf %s\\n "$PWD" >&2
command && cd "$OLDPWD" ||
! break; done || ! cd - >&2
The above command doesn't need to do any subshells - it just tracks its progress in the current shell by alternating $OLDPWD and $PWD. When you cd - the shell exchanges the value of these two variables, basically, as it changes directories. It also prints the name for each directory as it works there to stderr.
I just had a second look at it and decided I could do a better job with error handling. It will skip a dir into which it cannot cd - and cd will print a message about why to stderr - and it will break w/ a non-zero exit code if your command does not execute successfully or if running command somehow affects its ability to return to your original directory - $OLDPWD. In that case it also does a cd - last - and writes the resulting current working directory name to stderr.
Method 1 :
for i in `ls -d ./*/`
do
cd "$i"
command
cd ..
done
Method 2 :
for i in ./*/
do
cd "$i"
command
cd..
done
Method 3 :
for i in `ls -d ./*/`
do
(cd "$i" && command)
done
I hope this was useful. You can try all permutation and combinations on this.
Thanks :)
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1Welcome to the site, and thank you for your contribution. Please note, however, that parsing the output of
lsis highly disrecommended as it can stumble on directory names with whitespace or other special characters, so promoting method 1 and 3 without a warning might not be a good idea.AdminBee– AdminBee2021-01-26 08:17:17 +00:00Commented Jan 26, 2021 at 8:17