1exec [ -cl ] [ -a argv0 ] simple command 2 Replace the current shell with an external command rather than 3 forking. With -c clear the environment; with -l prepend - to 4 the argv[0] string of the command executed (to simulate a login 5 shell); with -a argv0 set the argv[0] string of the command exe- 6 cuted. See the section `Precommand Modifiers'. 7