Exit a shell script with status
n (e.g., exit 1).
n can be 0 (success) or nonzero (failure).
n is not given, exit status will be that of the most recent command.
exit can be issued at the command line to close a window (log out).
if [ $# -eq 0 ]; then echo "Usage: $0 [-c] [-d] file(s)" exit 1 # Error status fi