Question

I’m building a library, but I also want it to be usable as a standalone binary.

For example, let’s say I’m building an implementation of Tar. Tar is commonly used as a command, but it can also be used as a library. Intuitively, I’d do something like this:

src/
    tar/
        tar.go # belongs to package tar
        main.go # imports tar and provides a main function

This doesn’t seem to work though. From the documentation, it seems that “commands” should have a separate name from the library. Adapting the example given there to this example, I have the following directory structure:

src/
    tar/
        tar.go # belongs to package tar
    tarbin/
        main.go # imports tar and provides a main function

However, this creates a command called tarbin, not tar in $GOPATH/bin. The workaround I’ve found is to do go build -o $GOPATH/bin/tar tar, but I get the feeling I’m doing something horribly wrong. Is there a better way?

Note: I’m well aware that tar is included in the standard libs, I’m only using it as an example.

Answer 1

I’d probably do this

src/
    tar/
        tar.go         # tar libary
        tar/
            main.go    # tar binary

That will give you a binary called tar and a library called tar

Let’s say you are hosting this on github then you’d want

src/
    github.com/
        you/
            tar/
                tar.go         # tar libary
                tar/
                    main.go    # tar binary

Which would give you a binary called tar when you do go get install github.com/you/tar/tar and a library called github.com/you/tar when you do go get install github.com/you/tar

Depending on which you feel is more important you could swap the library and the binary over

src/
    github.com/
        you/
            tar/
                main.go            # tar binary
                tar/
                    tar.go         # tar libary

Keeping all the code in one tree enables you to do go install ./... from the root to build all packages and subpackages which is an advantage. go test|fmt ./... also. (Note that really is 3 dots!)