cd into all directories, execute command on files in that directory, and return to previous current directory

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?

Answers:

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Method 1

for d in ./*/ ; do (cd "$d" && somecommand); done

Method 2

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.

Method 3

for D in ./*; do
    if [ -d "$D" ]; then
        cd "$D"
        run_something
        cd ..
    fi
done

Method 4

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 5

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 🙂

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0