scripting

Handy toolset when using Go as a shell script replacement

CAVEAT EMPTOR

The API is still very unstable.

DESCRIPTION

Using Go to automate administrative tasks (e.g. deployment) is actually quite useful. Except, doing something as trivial as execute a command, and then grep for a particular pattern doesn't feel as easy as writing a real shell script.

We can not just make everything magical like shell, but we can make certain operations a bit easier. That is what these libraries are for.

EXECUTING A SIMPLE COMMAND

If you don't care to capture stdout or stderr, and all you care if the command runs successfully, you can use the shorthand cmd.Exec

  cmd.Exec("make", "install")

ADVANCED USAGE

You can create a cmd.Command instance by using cmd.New

  c := cmd.New("ls", "-l")

You can all cmd.Do to execute this command. Either pass nil, or the context.Context that you would like to use

  res, err := c.Do(nil)

The first return value is an instance of cmd.Result. It will contain information on the result of executing the command, such as captured output.

Output is not captured by default. You must explicitly state to do so.

  c.CaptureStdout(true)
  c.CaptureStderr(true)
  res, _ := c.Do(nil)
  fmt.Println(res.OutputString())

You can run certain filters on your output, such as Grep

  c.Grep(`regular expression pattern`)

If you specify this before callin Do(), your result output will be filtered accordingly.

Finally, this was getting really long. To avoid having to type everything in separate method calls, you can chain them all together

  res, err := cmd.New("ls", "-l").
    CaptureStdout(true).
    CaptureStderr(true).
    Grep(`regular expression pattern`).
    Do(nil)

For other options, please consult the godoc.