If you have been programming with golang, you’ve probably heard of cobra. I use it extensively at work and also in my personal projects.
Recently though, I’ve been using glog more and more. And I quite like it. The thing is, it has a couple of flag definitions in its init() function using golang’s builtin flag library. And I wanted to include those flags into cobra’s flag definitions. This is how I did it.
Generated help information will now look something like this.
# run the help command
$ ./cobraglog -h
Use glog with cobra.
Usage:
[flags]
Flags:
--alsologtostderr log to standard error as well as files
--echo string echo string (default "hello")
--log_backtrace_at traceLocation when logging hits line file:N, emit a stack trace (default :0)
--log_dir string If non-empty, write log files in this directory
--logtostderr log to standard error instead of files
--stderrthreshold severity logs at or above this threshold go to stderr (default 2)
-v, --v Level log level for V logs
--vmodule moduleSpec comma-separated list of pattern=N settings for file-filtered logging
-h, --help help for this command
Note that our cobra-defined flag --echo is also there. The rest are defined by glog internally. Finally, run the application.
# run the binary, providing the logtostderr flag defined by glog
$ ./cobraglog --logtostderr
I1129 13:49:34.166660 2138 main.go:28] echo (info): hello
W1129 13:49:34.166718 2138 main.go:29] echo (warn): hello
E1129 13:49:34.166722 2138 main.go:30] echo (error): hello
Here’s another example using subcommands.