You can start a sub-shell from the main edit screens at any time. This can be useful to compile a program, check for files, etc.
After executing [Esc][!] a popup window will prompt for a shell command. If you just press [Enter] with no other input, you will enter an interactive shell. If, on the other hand, you enter anything, it will be assumed to be a shell command and, as such, it will be passed to a shell for execution.
The shell used is that defined in the shell variable $SHELL. If this is not defined, the default shell ``/bin/sh'' will be used.
Sub-shells can be combined with macros to develop powerful new commands. For example, it is easy to define a macro as follows:
Macro M `XSAVE_BUFFER'`10'`DOSHELL'make`10'
which will save the current file and then call ``make'' to compile.