Why does running my globally npm linked package simply open the bin file?

Question

If I'm developing the npm package foo and I want it to be globally installed as a command-line application, I can do this simply by adding to my package.json:

"bin": {
    "foo": "./bin/foo.js"
}

Somebody who installs my package globally via npm will have the appropriate batch file and shell script added to their global npm prefix directory. However, suppose I want to be able to launch my package from the shell (or, in the case of Windows, the command prompt). I could do this by creating a batch file/shell script somewhere in one of my PATH directories that simply directly runs my package e.g. @node C:\my\package\directory\bin\foo %*.

This is a fairly simple and obvious solution, but I felt that npm link was better suited, as it feels less hacky and is theoretically designed to do this exact thing. I run npm link in my package directory, then test it by running foo from the command line. Rather than executing my script, though, foo.js is actually opened in my default editor. Investigating in the prefix directory, it turns out that the foo.cmd file (the contents of the foo shell script are similar) that npm created contains this:

"%~dp0\node_modules\foo\bin\foo.js"   %*

Compare with the batch file created by npm install -g:

@IF EXIST "%~dp0\node.exe" (
  "%~dp0\node.exe"  "%~dp0\node_modules\npm\bin\npm-cli.js" %*
) ELSE (
  @SETLOCAL
  @SET PATHEXT=%PATHEXT:;.JS;=;%
  node  "%~dp0\node_modules\npm\bin\npm-cli.js" %*
)

Why does npm link produce script files that launch a package's bin file instead of launching node with the bin file as an argument? How can I fix this behavior?

Answer 1

The solution is to add #!/usr/bin/env node at the beginning of your bin script. I have no idea why though. I found out by comparing my script to others that worked.