SYSTEM ["Command"]
SYSTEM /PROCESS Process_Name
The recommended use of the SYSTEM command is without any argument. In this case, SIC either creates a sub-process or attaches the terminal to a sub-process previously created. The created sub-process has originally the prompt $$. To return to the SIC monitor, type QUIT. Next SYSTEM commands will attach to the same sub-process which is not deleted when the program using SIC stops. It is recommended to use this form, rather than the command with argument, because it avoids the overhead of creating one sub-process per command. The sub-process is just created once.
Before attempting a new process creation, SIC identifies the existing subprocesses, and prompts you to which one you want to attach. Press the RETURN key if you want to create a new one.
In addition, you can attach to other processes created by other programs or commands using the SYSTEM /PROCESS command. In this case, to return to SIC you have to issue a VMS command ATTACH Prcnam where Prcnam is the name of the process which is running SIC (Use the VMS command SHOW PROCESS /SUBPROCESS to determine the process name Prcnam). QUIT will usually not work (although it may).
With arguments, the SYSTEM command effectively activates any valid VAX-VMS command by creating a temporary sub-process executing the requested command. Control is returned to SIC after completion of the command. This mode is not recommended because of the overhead required to create the process. For example you may issue the command
SIC> SYSTEM DIR
to list your current directory. Note that you cannot modify a local
assignation in this way because of the specificities of the sub-process.
Quotes are usually not necessary to delimitate the command passed to VMS; the only exception concerns the options, for which you must
avoid confusion between SIC and SYSTEM.
SIC> SYSTEM "DIR /FULL *.PRO" is perfectly valid
SIC> SYSTEM DIR /FULL *.PRO will produce the message
E-INTER, Unknown option /FULL for command SYSTEM