case $# in 1) prep $1 | sort -u | comm -23 - /usr/lib/dict/words ;; 3) if [ x$1 = "x-d" ] then if [ ! -r /usr/lib/dict/$2 ] then echo The dictionary file /usr/lib/dict/$2 is not readable exit fi prep $3 | sort -u | comm -23 - /usr/lib/dict/$2 else echo Usagex: spell [-d dict] file fi ;; *) echo Usage: spell [-d dict] file ;; esac