demand -- An easy way to install apps

demand will download, build, cache and run a Go app.

You can use it as an interpreter. Create a file bytes2human with that contains:

#!/usr/bin/env demand
go:
  import: github.com/tv42/humanize-bytes/cmd/bytes2human

The format is YAML.

And then run:

chmod a+x bytes2human

And now you can run that app with just:

./bytes2human 65536
64KiB

If you put that directory in your PATH, the dot and slash won't be needed anymore.

On first run, the source is downloaded, the app is built, and so on. On later runs, a cached copy of the resulting binary is used.

All command line arguments are passed to the underlying command. To pass flags to demand itself, always place them first, before any YAML file name.

Caching

Built binaries are stored in ~/.cache/demand/bin/${GOOS}_${GOARCH}/. Sharing the cache across different operating systems and architectures is safe. The cache directory is assumed to have atomic file renames.

Upgrading

If you want to grab a newer version of an app installed with demand, run:

demand -build -upgrade NAME

where NAME is one of:

• a command using demand as an interpreter (searched through PATH)

• a filename of the YAML mentioned above

To force NAME to be interpreted as a filename and not searched, include a slash in it; e.g. ./foo for relative paths.

Security

demand by default runs code controlled by whoever controls the import url. This is unsafe.

However, the default is no different from a go get followed by e.g. go test or running the built binary or using the library. Or a git clone ... && cd ... && make. So that may be just fine for you.

Developing commands

If you want to use demand to run commands without uploading the source to Github and such, you can tell demand to build and cache the package using your current GOPATH:

demand -build -upgrade -gopath bytes2human

Build results and missing dependencies are still written to a temporary directory.