General Commands

• man command : Gives information from the UNIX manual about command. Text is displayed using less(below).
  Also, man -k word will list manual pages whose titles contain the keyword word.
• Ctrl+C : Usually kills whatever you are doing and signals the shell to accept the next command. Use Ctrl+C only if you are stuck, since work you did during the killed command may be lost.
• Ctrl+Z : This control code temporarily suspends a command, whereupon the shell can accept the next command. Use the fg (foreground) command to get the suspended process running again; type jobs to see if you have any suspended or background processes. Or use the bg command to have the last suspended job run in the background.
• date :Displays the current date and time.
• finger name : Looks up the user information of the user matching name, e.g. finger Gilfong will return a list of users matching whose first name, last name, or username match Gilfong.
• gzip file : Compresses file. The full-size file is removed and the compressed file has the same name with an extension of ".gz" added. You can get 4 to 1 compression on low-entropy data.
• gunzip file :The inverse of gzip: restores the original file.
• hostname : Gives the name of the computer on which you are currently working.
• kill pid : Cancel the process with identification pid
• pkill process : Cancel the named process - e.g. pkill mybustedscript
• less : Displays text files one page at a time. Press "h" for help, "q" to quit", SPACE to go to the next page, "b" for previous page, "/" to search, etc.
• logout : Ends your session.  If you ran multiple shells you may need to run this for each nested process. CTRL-D from a shell prompt does the same.
• locate file : gives the location of file based on the contents of a database which is updated nightly. 
• nice -prior program : Gives program processing priority value prior (1 being the highest priority level and 19 the lowest) which tells the computer how to process tasks.
  e.g. nice -19 ./a.out & runs the program a.out in the background at the lowest priority.
• passwd : Changes your password. You will be asked to type the old password first, and then the new password twice. None of this is visible on the screen.
• command1 | command2 : Called the “pipe” command. Takes the output of command command1 and uses it as the input for command2.
  e.g. ls | less lists files in the current directory and views the results in a paginated form
• uptime : Shows the load on the computer you are currently using.
• who : Lists all users on the computer in which you are currently working.
• whoami : Tells who is currently logged on a specific terminal