AmendStringAry where []string (like os.Environ()) is string of key=value pairs.

NewUsage Set up the application usage information.

PrintUsage Display application usage information.

RunCommand run an external program in a sub process.

RunCommandWithInput run an external program in a sub process, allowing with input.

RunCommandWithInputAndEnv run an external program in a sub process, with input and setting environment variables in the sub process.