[basename] remove extra whitespace
[cat] change c from char to int
[cut] add cut
[date] add date
[dd] add dd
[dirname] add dirname
[date] add custom date format
[echo] add echo
[env] add env
[basename] make POSIX compliant
[cat] add (ignored) "-u" option
[chmod] add chmod
[misc] fix compiler warnings
[chmod] add default case in option parsing
[mv] add mv
[misc] fix error string order
[rm] add rm
[rmdir] add rmdir
[comm] add comm
[ln] add ln