getOption("system_cmd"). A OS agnostic interface to the system
terminal. Most of the time this will be the same as
system_nm except when
the PsN/NONMEM execution server is location in a different location to the
system_cmd(cmd, dir = ".", ...)
Character. Command to send to shell.
Optional character. Directory to run command in (default = current working directory)
Other arguments passed to system command.
The return value of