Usage:
/SYS shell-command
Executes shell-command. The command is executed without a tty, so it should have no input, and its output, if any, should be plain text. The command's stdout and stderr are echoed to tf's output window. /sys differs from /sh in that /sys can not do an interactive shell command, but does not redraw the screen or produce any extra messages.
Note: calling /sys with arguments from a trigger is dangerous. If not written carefully, such a trigger could allow anyone with access to the server to gain access to your shell account.
The return value of /sys is the exit status of the shell if it exited normally, -1 otherwise. Note that UNIX shell commands usually return 0 for success and nonzero for failure, which is the opposite of the TF convention.
/sys executes synchronously. To execute a command asynchronously (in the background), use /quote without the -S option.