Bash：如何控制迭代流/循环？

Question

For going over some recovered data, I am working on a script that recursively goes through folders & files and finally runs file on them, to check if they are likely fully recovered from a certain backup or not. (recovered files play, and are identified as mp3 or other audio, non-working files as ASCII-Text)

For now I would just be satisfied with having it go over my test folder structure, print all folders & corresponding files. (printing them mainly for testing, but also because I would like to log where the script currently is and how far along it is in the end, to verify what has been processed)

I tried using 2 for loops, one for the folders, then one for the files. (so that ideally it would take 1 folder, then list the files in there (or potentially delve into subfolders) and below each folder only give the files in that subfolders, then moving on to the next. Such as:

Folder1  
- File 1  
- File 2  
    -- Subfolder  
    -- File3  
    -- File4  
Folder2  
- File5  

However this doesn't seem to work in the ways (such with for loops) that are normally proposed. I got as far as using "find . -type d" for the directories and "find . -type f" or "find * -type f" (so that it doesn't go in to subdirectories) However, when just printing the paths/files in order to check if it ran as I wanted it to, it became obvious that that didn't work.

It always seemed to first print all the directories (first loop) and then all the files (second loop). For keeping track of what it is doing and for making it easier to know what was checked/recovered I would like to do this in a more orderly fashion as explained above. So is it that I just did something wrong, or is this maybe a general limitation of the for loop in bash?

Another problem that could be related: Although assigning the output of find to an array seemed to work, it wasn't accessible as an array ...

Example for loop:
for folder in '$(find . -type d)' ; do
echo $folder
let foldercounter++
done

Arrays: folders=("$(find . -type d)")
#As far as I know this should assign the output as an array
#However, it is not really assigned properly somehow as
echo "$folders[1]"
# does not work (quotes necessary for spaces)

Answer 1

For going over some recovered data, I am working on a script that recursively goes through folders & files and finally runs file on them, to check if they are likely fully recovered from a certain backup or not. (recovered files play, and are identified as mp3 or other audio, non-working files as ASCII-Text)

If you want to run file on every file and directory in the current directory, including its subdirectories and so on, you don't need to use a Bash for -loop, because you can just tell find to run file :

find -exec file '{}' ';'

(The -exec ... ';' option runs the command ... on every matched file or directory, replacing the argument {} with the path to the file.)

If you only want to run file on regular files (not directories), you can specify -type f :

find -type f -exec file '{}' ';'

If you (say) want to just print the names of directories, but run the above on regular files, you can use the -or operator to connect one directive that uses -type d and one that uses -type f :

find -type d -print -or -type f -exec file '{}' ';'

---

Edited to add: If desired, the effect of the above commands can be achieved in pure Bash (plus the file command, of course), by writing a recursive shell function. For example:

function foo () {
    local file
    for file in "$1"/* ; do
        if [[ -d "$file" ]] ; then
            echo "$file"
            foo "$file"
        else
            file "$file"
        fi
    done
}
foo .

This differs from the find command in that it will sort the files more consistently, and perhaps in gritty details such as handling of dot-files and symbolic links, but is broadly the same, so may be used as a starting-point for further adjustments.

Answer 2

A find ... -exec ... solution @H.-Dirk Schmitt was referring to might look something like:

find . -type f -exec sh -c '
    case $(file "$1") in
    *Audio file*)
        echo "$1 is an audio file"
        ;;
    *ASCII text*)
        echo "$1 is an ascii text file"
        ;;
    esac
' _ {} ';'