#GREP
1. grep -E '(\w)\1' /etc/passwd
2. grep -E '([a-z]\1' /etc/passwd

#CHMOD
1. # don't see last part, 2 might be wrong because of this
2. chmod u-r,o+w homework

#FIND
1. find ~ -type f

#KILL
kill terminates a process. For example if we had vim process running with process id (pid) 2550, then we can kill the process by running: kill 2550

#IO
1. find /usr/bin/ 2>find.err >$HOME/find.out
2. ps -ef > /tmp/ps.out.$$