alias: allows launching of any command or combination of commands by using a preset character or series of characters.
cat: (short for concatenate) has three related functions with regard to text files: displaying them, combining copies of them and creating new ones.
ps: (short for process status) lists the currently running processes and their process identification numbers (PIDs).
su: (short for substitute user) changes a login session's owner without the owner having to first log out of that session.
uptime: shows the current time, how long the system has been running since it was booted up, how many user sessions are currently open and the load averages.
whatis: provides very brief descriptions of command line programs and other topics related to Unix-like operating systems.
________ The above commands are those that are described in detail by The Linux Information Project. They represent only a fraction of the total number of standard commands typically included in Linux and other Unix-like operating systems. In keeping with the Unix philosophy, most are small, independent, and highly specialized programs.