N defaults to 10, but should be settable with a command-line option "-cols N".
If command-line arguments are provided, the program should treat them as files to be read instead of using stdin.
The command-line option "-u" tells the program to unscramble instead. Also, if the program is invoked with the name "unscramble" rather than "scramble", it should behave as though it had been given the "-u" option.
The "-u" and "-cols N" options may be given in either order, but will be separate words on the command line (i.e. you don't have to handle "-ucols 6"), and will appear before any filename arguments.
panther% scramble >msg This is a test of the emergency broadcasting system. This is only a test. ^D panther% cat msg Tteytmhe i.isebn stmrg eo ioras sfgdy ecs atnat hcse Tlhyi sa itse sotn. panther% scramble -u <msg This is a test of the emergency broadcasting system. This is only a test. panther% unscramble msg | scramble -cols 7 T nanehaoecdgmi fmyc .st e as etrbsy ishgrts steeoit T hotinesls yti .sa panther%