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Extract filename and extension in Bash

I want to get the filename (without extension) and the extension separately.

The best solution I found so far is:

NAME=`echo "$FILE" | cut -d'.' -f1`
EXTENSION=`echo "$FILE" | cut -d'.' -f2`

This is wrong because it doesn't work if the file name contains multiple . characters. If, let's say, I have a.b.js, it will consider a and b.js, instead of a.b and js.

It can be easily done in Python with

file, ext = os.path.splitext(path)

but I'd prefer not to fire up a Python interpreter just for this, if possible.

Any better ideas?

Answer*

### Magic file recognition

In addition to the lot of good answers on this Stack&nbsp;Overflow question I would like to add:

Under Linux and other unixen, there is a *magic* command named `file`, that do filetype detection by analysing some first bytes of file. This is a very old tool, initialy used for print servers (if not created for... I'm not sure about that).

    file myfile.txt
    myfile.txt: UTF-8 Unicode text

    file -b --mime-type myfile.txt
    text/plain

Standards extensions could be found in `/etc/mime.types` (on my [Debian][1] GNU/Linux desktop. See `man file` and `man mime.types`. Perhaps you have to install the `file` utility and `mime-support` packages):

    grep $( file -b --mime-type myfile.txt ) </etc/mime.types
    text/plain      asc txt text pot brf srt

You could create a [tag:bash] function for determining right extension.
There is a little (not perfect) sample:

    file2ext() {
        local _mimetype=$(file -Lb --mime-type "$1") _line _basemimetype
        case ${_mimetype##*[/.-]} in
            gzip | bzip2 | xz | z )
                _mimetype=${_mimetype##*[/.-]}
                _mimetype=${_mimetype//ip}
                _basemimetype=$(file -zLb --mime-type "$1")
                ;;
            stream )
                _mimetype=($(file -Lb "$1"))
                [ "${_mimetype[1]}" = "compressed" ] &&
                    _basemimetype=$(file -b --mime-type - < <(
                            ${_mimetype,,} -d <"$1")) ||
                    _basemimetype=${_mimetype,,}
                _mimetype=${_mimetype,,}
                ;;
            executable )  _mimetype='' _basemimetype='' ;;
            dosexec )     _mimetype='' _basemimetype='exe' ;;
            shellscript ) _mimetype='' _basemimetype='sh' ;;
            * )
                _basemimetype=$_mimetype
                _mimetype=''
                ;;
        esac
        while read -a _line ;do
            if [ "$_line" == "$_basemimetype" ] ;then
                [ "$_line[1]" ] &&
                    _basemimetype=${_line[1]} ||
                    _basemimetype=${_basemimetype##*[/.-]}
                break
            fi
            done </etc/mime.types
        case ${_basemimetype##*[/.-]} in
            executable ) _basemimetype='' ;;
            shellscript ) _basemimetype='sh' ;;
            dosexec ) _basemimetype='exe' ;;
            * ) ;;
        esac
        [ "$_mimetype" ] && [ "$_basemimetype" != "$_mimetype" ] &&
          printf ${2+-v} $2 "%s.%s" ${_basemimetype##*[/.-]} ${_mimetype##*[/.-]} ||
          printf ${2+-v} $2 "%s" ${_basemimetype##*[/.-]}
    }

This function could set a Bash variable that can be used later:

(This is inspired from @Petesh right answer):

    filename=$(basename "$fullfile")
    filename="${filename%.*}"
    file2ext "$fullfile" extension

    echo "$fullfile -> $filename . $extension"

  [1]: http://en.wikipedia.org/wiki/Debian

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2

Although not a direct answer to the original post, this is by far the most sensible response. Thanks for providing it.

mp035
– mp035

2021-01-06 05:23:30 +00:00
Commented Jan 6, 2021 at 5:23
I really appreciate this thorough answer highlighting common built-ins. Though I ended up just doing this in python using the -c flag, if I were constrained to using just shell scripting I'd use the concepts outlined herein. Thank you!

Jason R Stevens CFA
– Jason R Stevens CFA

2022-04-10 02:26:30 +00:00
Commented Apr 10, 2022 at 2:26
@JasonRStevensCFA under python, you will use python-magic library!

F. Hauri - Give Up GitHub
– F. Hauri - Give Up GitHub

2022-04-10 05:52:22 +00:00
Commented Apr 10, 2022 at 5:52
@F.Hauri Cool lib, thanks for sharing. I just use standard stuff as the string builtins for scripting are beyond simple. For example, $(python -c "'$1'.split('/')[-1]") will get you the filename with extension from a path string variable $1 using a subshell (I use it like this in some local scripts). I don't use this kind of "magic" in prod but these features of the Python language are fantastic for simple task-based things.

Jason R Stevens CFA
– Jason R Stevens CFA

2022-04-10 20:15:18 +00:00
Commented Apr 10, 2022 at 20:15
@JasonRStevensCFA Using forks to python, like any other language (perl, awk, etc...) for so tiny requirment is counter-productive! Try to run same fork 1000 time and compare with parameter expansion...

F. Hauri - Give Up GitHub
– F. Hauri - Give Up GitHub

2022-04-11 21:27:44 +00:00
Commented Apr 11, 2022 at 21:27

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Extract filename and extension in Bash

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