DISCOVERY EXERCISES

$1.$ Use the whatis command to determine the purpose of the ls command.

$2.$ Use the man program to find out what the $-$R option does when used with the date

command.

$3.$ Use the man program to determine what other commands you should also see in

relation to the clear command.

$4.$ Use the cal command to determine on what day of the week you were born.

$5.$ Use the cal command to determine which years between $2006$ and $2015$ are leap years.

$6.$ Clear the screen, and view the online manual to determine how to display today$$s

date in UTC.

$7.$ Display the current UTC.

$8.$ Create a file called month containing the current month.

$9.$ View the contents of the month file you created in Exercise $8.$

$10.$ Use the who command to determine the idle time for users currently logged in$,$ but

output that information to a file called users$\_$info. Next, view the file you created.

Figure $1-20$ Viewing the contents of the notes file

Discovery Exercises $51$

$1$

$11.$ View the files, month and users$\_$info, in sequence using only one command$-$line

sequence of commands.

$12.$ View the files month and users$\_$info in sequence by using:

The less command

The more command

$13.$ Create a file called who$\_$info that contains the documentation for the who

command. Next, use the less command to view the who$\_$info file contents, and scroll

forward and backward through the information. Then use the tail command to view

the final $12$ lines of the who$\_$info file. Finally, use the head command to view the

first $12$ lines of the who$\_$info file.

$14.$ Create a file called favorite$\_$foods, and list your favorite foods, entering five or six or

more. Press Enter after each favorite food so it appears on its own line $($make certain you

also press Enter after the final food item$).$ After the file is created, add two more foods

you like that are not on the list $($press Enter after the final food item$).$ View the list of

foods to make certain the two items you added appear at the end of the list.

$15.$ View the documentation for who, and then view the documentation for w$.$ How are

these commands similar?

$16.$ Run the who $-$uH and w commands using one command$-$line sequence to compare

the results.

$17.$ Determine when the computer on which you are working was last booted.

$18.$ Use the command$-$line history function to determine the most recent two commands you entered.

$19.$ Run the who $-$H$,$ cal $2009,$ and clear commands using one command$-$line sequence.

What do you end up with on the screen?

$20.$ Use the history function to retrieve the command line you used in Exercise $19.$ Use

the edit function to remove the word $$clear$$ and replace it with $$date$.$ Next, go to

the beginning of $$cal$$ and delete the text on the line from $$cal$$ to the end. Now,

change the $-$H to $-$u$.$ Finally, add $$date $-$u$$ so that your final command$-$line entry is

who $-$u ; date $-$u$.$ Execute the command$-$line entries.