`swift sh`

Writing Swift scripts is easy:

$ cat <<EOF > script
#!/usr/bin/swift
print("Hi!")
EOF
$ chmod u+x script
$ ./script
Hi!

Sadly, to use third-party dependencies we have to migrate our script to a swift package and use swift build, a relatively heavy solution when all we wanted was to whip up a quick script. swift-sh gives us the best of both worlds:

$ cat <<EOF > script
#!/usr/bin/swift sh
import PromiseKit  // @mxcl ~> 6.5
print(Promise.value("Hi!"))
EOF
$ chmod u+x script
$ ./script
Promise("Hi!")

In case it’s not clear, swift-sh reads the comment after the import and uses this information to fetch your dependencies.

Let’s work through an example: if you had a single file called foo.swift and you wanted to import mxcl/PromiseKit:

#!/usr/bin/swift sh

import Foundation
import PromiseKit  // @mxcl ~> 6.5

firstly {
    after(.seconds(2))
}.then {
    after(.milliseconds(500))
}.done {
    print("notice: two and a half seconds elapsed")
    exit(0)
}

RunLoop.main.run()

You could run it with:

$ swift sh foo.swift

Or to make it more “scripty”, first make it executable:

$ chmod u+x foo.swift
$ mv foo.swift foo    # optional step!

And then run it directly:

$ ./foo

Installation

brew install mxcl/made/swift-sh

Or with Mint:

mint install mxcl/swift-sh

Or you can build manually using swift build.

Installation results in a single executable called swift-sh, the swift executable will call this (provided it is in your PATH) when you type: swift sh.

We actively support both Linux and Mac and will support Windows as soon as it is possible to do so.

Support mxcl

Hi, I’m Max Howell and I have written a lot of open source software, and probably you already use some of it (Homebrew anyone?). Please help me so I can continue to make tools and software you need and love. I appreciate it x.

Other donation/tipping options

Usage

Add the shebang as the first line in your script: #!/usr/bin/swift sh.

Your dependencies are determined via your import lines:

#!/usr/bin/swift sh
import PromiseKit  // @mxcl ~> 6.5
import Foo         // @bar == 6.5
import Baz         // @bar == b4de8c
import Floobles    // mxcl/Flub == master
import BumbleButt  // https://example.com/bb.git ~> 9

swift-sh reads the comments after your imports and fetches the requested SwiftPM dependencies.

The above will fetch:

https://github.com/mxcl/PromiseKit, the highest available version that is greater than or equal to 6.5.0 but less than 7.0.0
https://github.com/bar/Foo version precisely 6.5.0
https://github.com/bar/Baz, with the specific Git SHA b4de8c
https://github.com/mxcl/Flub, master branch
https://example.com/bb.git, highest available version 9.0.0..<10.0.0

It is not necessary to add a comment specification for transitive dependencies.

Examples

Converting your script to a package

Simple scripts can quickly become bigger projects that would benefit from being packages that you build with SwiftPM. To help you migrate your project we provide swift sh eject, for example:

$ swift sh eject foo.swift

creates a Swift package in ./Foo, from now on use swift build in the Foo directory. Your script is now ./Foo/Sources/main.swift.

Use in CI

If you want to make scripts available to people using CI; use stdin:

brew install mxcl/made/swift-sh
swift sh <(curl http://example.com/yourscript)

Internal Details

swift sh creates a Swift Package.swift configured to fetch your dependencies and build a single executable for your script in ~/Library/Developer/swift-sh.cache†, the script is then executed via swift run.

† We use the FreeDesktop specified cache location on Linux.

TODO

More types of version specifications
Removing SwiftPM output unless there are errors
Optimizing the cache (creating a library structure more like gem or pip would)
Error out if the import specification is invalid, currently we silently ignore such lines

Limitations

Our logic for determining package modules is insufficient. It works for most packages, but will fail for packages with multiple modules. I’ll fix this once I need to, but feel free to PR it. Doing this properly is probably easiest if we depend on SwiftPM itself and use its machinery to get module information.

Alternatively we could require all imports that a script depends on to be specified in the form that we already do. Or we could assume all imports that are not Apple imports to be dependencies for the generated Package.swift. Or we could manage the build ourselves which isn’t too hard and would be the solution that simplifies our system the most.

If you have two scripts with the same name we will (currently) always need to rebuild whenever you rotate between them.

Alternatives

Get push notifications for new releases

https://codebasesaga.com/canopy/

Troubleshooting

`error: unable to invoke subcommand: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-sh`

If you got here via Google, you have a script that uses this tool, if you now install swift-sh, you will be able to run your script:

brew install mxcl/made/swift-sh

Or see the above installation instructions.

unnamedd / swift-sh