add .sh extension to all bash files

Question

I have a directory containg several files, including those files some are bash scripts but their name doesn't include the .sh extension. I know I need to use the file command to know the type of files with -type option, I also know that I can redirect the output with xargs so I can rename the files with their origianl name + the .sh extension. The problem is I don't know how to pipe all the commands together, and how to find files type of only bash ASCII text executable. Any idea how to do that with a simple command?

Answer 1

although that is not fulfilling your homework there is no need for find as grep kann search directories for files recursively with -r (and even that is not needed when file names are passed with globbing)

grep -lIw '^#!.*bash' dir/!(*.sh) | xargs -I_ mv _ _.sh

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grep -r dir will search all files in all subdirectories (not used here)

grep -l is similar to -H print the file name for each match, but suppress normal output. furthermore it stops after first match similar to -q or -m1

grep -I exclude binary files, process text files only

grep -w bash will match whole word only (won't match bashed)

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regex ^ #! match begin of line only (won't match ##!)

regex . match any byte * any occurrence = .* any string

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pathname expansion (globbing) *.sh matches pattern file.sh

extended globbing !(pattern) matches anything except pattern

ls dir/!(*.sh) list all files in dir excluding dir/file.sh files

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xargs -I pattern will insert arguments on each position pattern is used _ in this example:

mv   _     _  .sh
mv file1 file1.sh
mv file2 file2.sh

Answer 2

If you've set up any of the standard shebang lines it looks like file (at least version 5.39) should be able to detect them:

$ echo '#!/usr/bin/env bash' > 1
$ echo '#!/bin/bash' > 2
$ echo '#!/usr/bin/bash' > 3
$ file *
1: Bourne-Again shell script, ASCII text executable
2: Bourne-Again shell script, ASCII text executable
3: Bourne-Again shell script, ASCII text executable

So we should be able to do this:

for path in ./*
do
    if [[ "$(file "$path")" = "${path}: Bourne-Again shell script, ASCII text executable" ]]
    then
        mv "$path" "${path}.bash"
    fi
done

This works for the above example files (and should work for unusual filenames, including those containing space characters, starting with a hyphen, or ending with a newline):

$ ls
1.bash  2.bash  3.bash

This will probably not work if your files do not have shebang lines (which is reasonable for files which are sourced by other scripts or the shebang lines are wrong (such as #!/bin/sh).

(I've used ".bash" since that is more explicit than ".sh".)