macOS: Double click on a file and display the output from a CLI command on the file?

Question

There is a file type called "netCDF". My goal is to be able to double click on a netCDF file on Finder and see the text output from a CLI command to which the filename is given.

Specifics: There is a command-line command that displays the table of contents of a netCDF file:

$ ncdump -h yourfile.nc

This command shows the table of contents of the netCDF file to the current terminal.

How can I see the same output when I double click on the file on Finder?

Edit: The following is a description of a failed approach.

I have made some progress toward a solution.

Following this thread

How to make a Mac OS X .app with a shell script?

I've been able to create a macOS "app" which is actually a shell script:

#!/bin/sh
/usr/local/bin/ncdump -h "$@"

So far, I've been able to verify that I can invoke this "app" from Finder and that the above shell script is actually run. But, I found that the shell script doesn't get the filename as a command line argument. (You can see what's going on by modifying the line to /usr/local/bin/ncdump -h "$@" > $HOME/tmp/logfile.txt 2>&1)

So, I have two specific questions

1. How can a shell script (as app) get the filename when invoked from Finder?

2. To which GUI app should it send its stdout and how?

Answer 1

If your App is actually just a shell script, you don't need the open command to run it. Just execute the shell script using ./PATH_TO_SCRIPT -- in your case, this would be ./MyApp.app/MyApp, if you followed the naming suggested in the linked thread. From there, you can redirect or pipe the output like with any other shell command.

However, if you have to use the open command: There seems to be an argument --stdout, which could solve your problem. From man open:

--stdout PATH
    Launches the application with stdout connected to PATH.

Edit

The edit of your question changes a lot: You want to start the Application/Script via Finder, but then see the "Terminal Output".

You could, for example, use AppleScript to show a notification or dialog containing the output of your app (depending on how much text it is). This can be done using the osascript -e '[APPLESCRIPT_COMMANDS]' command. For example, osascript -e 'display dialog "Sample Text"' will show a small popup window containing "Sample Text" and Ok/Cancel buttons. More info on dialogs can be found for example here.

For this to work, you must redirect the output of the commands in your script to a variable, this can be done for example with myVariable=$(...original command...)

Answer 2

Abandoning the idea of turning a shell script into an app, I adopted @JLubberger's idea of using an AppleScript. The best I have achieved so far is

on open filename
    tell application "Terminal"
        do script "ncdump -h " & quoted form of POSIX path of filename & " 2>&1"
        activate
    end tell
end open

and export this as an app.

Then, open a netCDF file with this app, which will launch Terminal, which will show the output from the command "ncdump -h filename".

One unsatisfactory aspect to this solution is that Terminal shows extra ouptputs of its own. I'd rather have a window which will just show the ouptput from the command. This would be a different approach because I would have to find a way to run the command from within the script and send its output to a GUI window. In contrast, the above script of mine asks Terminal both to run the command and to display its output.