bin and vendor/bin

What is a bin?

Any command line script that a Composer package would like to pass along to a user who installs the package should be listed as a bin.

If a package contains other scripts that are not needed by the package users (like build or compile scripts) that code should not be listed as a bin.

How is it defined?

It is defined by adding the bin key to a project's composer.json. It is specified as an array of files so multiple bins can be added for any given project.

{
    "bin": ["bin/my-script", "bin/my-other-script"]
}

What does defining a bin in composer.json do?

It instructs Composer to install the package's bins to vendor/bin for any project that depends on that project.

This is a convenient way to expose useful scripts that would otherwise be hidden deep in the vendor/ directory.

What happens when Composer is run on a composer.json that defines bins?

For the bins that a package defines directly, nothing happens.

What happens when Composer is run on a composer.json that has dependencies with bins listed?

Composer looks for the bins defined in all of the dependencies. A symlink is created from each dependency's bins to vendor/bin.

Say package my-vendor/project-a has bins setup like this:

{
    "name": "my-vendor/project-a",
    "bin": ["bin/project-a-bin"]
}

Running composer install for this composer.json will not do anything with bin/project-a-bin.

Say project my-vendor/project-b has requirements setup like this:

{
    "name": "my-vendor/project-b",
    "requires": {
        "my-vendor/project-a": "*"
    }
}

Running composer install for this composer.json will look at all of project-b's dependencies and install them to vendor/bin.

In this case, Composer will make vendor/my-vendor/project-a/bin/project-a-bin available as vendor/bin/project-a-bin. On a Unix-like platform this is accomplished by creating a symlink.

What about Windows and .bat files?

Packages managed entirely by Composer do not need to contain any .bat files for Windows compatibility. Composer handles installation of bins in a special way when run in a Windows environment:

A .bat files is generated automatically to reference the bin
A Unix-style proxy file with the same name as the bin is generated automatically (useful for Cygwin or Git Bash)

Packages that need to support workflows that may not include Composer are welcome to maintain custom .bat files. In this case, the package should not list the .bat file as a bin as it is not needed.

Can vendor bins be installed somewhere other than vendor/bin?

Yes, there are two ways that an alternate vendor bin location can be specified.

Setting the bin-dir configuration setting in composer.json
Setting the environment variable COMPOSER_BIN_DIR

An example of the former looks like this:

{
    "config": {
        "bin-dir": "scripts"
    }
}

Running composer install for this composer.json will result in all of the vendor bins being installed in scripts/ instead of vendor/bin/.

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