There are three pairs of I/O handles in a shell process. The shell's Process structure contains the pr_CIS (current input stream) and pr_COS (current output stream) file handles. That Process's CommandLineInterface structure contains the other two pairs of I/O handles: cli_StandardInput/cli_StandardOutput and cli_CurrentInput/cli_CurrentOutput. Each has different uses within a normal shell. Routines that operate on Input() or Output(), such as ReadArgs() or ReadItem(), use the pr_CIS and pr_COS I/O handles (which they acquire by calling the dos.library routines Input() and Output(), not by directly looking at the Process structure). Shell-launched application programs the run on the shell's process also use these I/O handles as their normal input and output channels. This is where functions like scanf() and printf() get and send their input and output. The shell changes these file handles (using SelectInput()/SelectOutput()) according to the shell defaults and according to any I/O redirection. The cli_StandardInput and cli_StandardOutput I/O handles are the default input and output channels for the shell. They usually refer to the user's console window and will not change while the shell is running. The shell should use these values as the default values for pr_CIS and pr_COS (via SelectInput() and SelectOutput()) when it runs a command from a command line. The cli_CurrentInput handle is the current source of command lines. This normally is the same as cli_StandardInput. The cli_CurrentInput handle will differ from cli_StandardInput when the shell is executing a script or when handling an Execute() or System() call. In these cases, it points to a file handle from which the shell is reading commands. This handle refers to one of three files: the script file you called with the execute command, a temporary file created by the execute command, or a pseudo file created by Execute() or System(). When a shell runs the execute command, If cli_CurrentInput differs from cli_StandardInput, The execute command will close cli_CurrentInput and replace it with a new one, so don't cache the value of cli_CurrentInput as it will be invalid. In this case, cli_CurrentInput must not be the same as pr_CIS when you call RunCommand() if the executable could possible be the execute commands (or anything else that tries to close cli_CurrentInput). The cli_CurrentOutput file handle is currently unused by the system. It's initialized to the same as cli_StandardOutput.
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