_SHELL System Variable
Specifies a program shell.
_SHELL = cCommand
Remarks
The _SHELL system memory variable is used to prevent access to the Command window while a program is running in Visual FoxPro. The DO command with the name of a program to execute is usually stored to _SHELL.
You can also specify a command to execute when Visual FoxPro is started by placing the SHELL configuration item in your Visual FoxPro configuration file.
The following example demonstrates how _SHELL typically can be used.
A startup program named Mystart.prg is used to launch another program named Myapp.prg. Mystart.prg stores the command to run Myapp.prg to _SHELL. This starts Myapp.prg. Before Visual FoxPro displays the Command window, _SHELL is checked for a command. If _SHELL contains a command, it is executed and Visual FoxPro then stores the empty string to _SHELL.
After the initialization code in Myapp.prg is successfully executed, the command to launch Myapp.prg is stored again to _SHELL. Visual FoxPro does not execute the command or store the empty string to _SHELL, and access to the Command window is prevented. (The Command window cannot be accessed when _SHELL contains anything but the empty string).
Before Myapp.prg finishes execution, it stores the empty string to _SHELL to restore access to the Command window.
** MYSTART.PRG ** ... _SHELL = "DO MYAPP.PRG"
** MYAPP.PRG ** ** Initialization Code ** ... ** Initialization Code successfully completed? ** _SHELL = "DO MYAPP.PRG" && Prevents access to Command window ... ** Clean up Code ** _SHELL = ""