Embodiments described herein are based on the principle that shells execute commands as units of characters. Accordingly, embodiments herein provide also provide for some special cases of asynchronous control signals that change the shell operation flow. For example, signal messages may be used to terminate, pause, resume, or otherwise modify the execution of a command. In other words, if a user wishes to change the execution state of a command, a client can create a signal message and send such message to the shell processor, which can take the appropriate action as desired. Note that by modeling the control or signal commands as discrete messages (as well as other embodiments modeled and described herein), such commands are not mistakenly executed on a command as is the case for current protocols that use a character-by-character transmission.