NewCommand create a Command.

Run runs commands in parallel from channel chCmdStr， and returns a Command channel, and a done channel to ensure safe exit.

Run4Output runs commands in parallel from channel chCmdStr, and returns an output text channel, and a done channel to ensure safe exit.

bit mask.

pid_numSecondsSinceEpoch.

ErrCancelled means command being cancelled.

ErrTimeout means command timeout.

Log is *logging.Logger.

16K.

1M.

Verbose decides whether print extra information.

Command is the Command struct.

ImmediateLineWriter is safe to use concurrently.

from https://softwareengineering.stackexchange.com/questions/177428/sets-data-structure-in-golang.

Options contains the options.