go get和go install有什么区别？

After playing with the go tool for a while, it looks like go get:

  1. (optionally) downloads,
  2. compiles,
  3. and installs

a piece of software, while go install simply

  1. compiles
  2. and installs

it. In this case, why does the go install command exist, since go get supersedes it?

go install is part of the workflow when working locally. Say you want to use a library, but for some reason a change is required. You would do:

  • go get -d library, which only downloads it;
  • make the change on the downloaded package;
  • go install library to install the local version.

As far as I know go get has no flags to indicate it should not download, so it can't replace go install here.

The same workflow is used when you develop a new package from scratch.

go get does two main things in this order:

  • downloads and saves in $GOPATH/src/<import-path> the packages (source code) named in the import paths, along with their dependencies, then

  • executes a go install

The -d flag (go get -d) instructs go get to stop after downloading the packages; that is, it instructs go get not to do go install

the difference:

go get // verify if packages need to be downloaded, download if needed then compile

go install // skip the part with packages download, just compile (this will throw an error if any packages are missing)

about GOPATH environment variable

The GOPATH environment variable must be set in order to be able to get, build and install packages, and it specifies the location of your workspace. It is likely the only environment variable you'll need to set when developing Go code.

Again, the GOPATH should not point to the Go installation, but rather to your workspace.

For example, on Windows, if you decide that your workspace is at c:\gowork\, you will need to set GOPATH value as c:\gowork

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Your source code should be at c:\gowork\src\<some project folder>\ and after you run go get at command prompt from within c:\gowork\src\<some project folder>\ you will see the c:\gowork\bin\ and c:\gowork\pkg\ being created.