Shell

The shell command checks the environment variable SHELL and tries to run a program of the name found there or gulam.prg, if not SHELL entry is present.

The ! command first checks whether a shell is already loaded (shell_p) or tries to call the command directly.

When in guläm !ls give a directory, even if no ls program is present.

!cd might work with certain shells, but the use of the gnuplot cd is recommended.