Linux Essentials 2.0 Chapter 11 Exam Answers

n n 0C ap er 1 1 Ex am A sw e LLiiinu in nux u ux xE Essse en nti ntttia ial alls 2 2...0 Ch ha p pttte er 11 xa am An n nsw wer ers rs s 11 be hiss m 1. A ffi file eb beg egi eg gins nss w wit it ith th #!/bin/csh. T This mea eans ns ns: wi me This is a Perl script The operator should not be using /bin/csh C Shell compatibility mode is enabled Running the script will invoke /bin/csh to interpret the rest of the file Nothing, this is a comment • • • • • 22 are a ttor 2. Wh Whi hic ich are appro p rop pri rri ria ia iat at ate ee edi d diiitto orss ffor orr w wri rriiting t g sh she hel elllll sscr cri crrip riipt p ptts? ss? ed o wr (c hoos ttwo (cho ch hoo ose se tw w wo o)) Firefox /bin/bash LibreOffice Writer vi nano • • • • • 33 Mo omma ke tth 3. Mos ost stt of nano’s ’s ccomm co man ma and n nd dss ta take the he fo form rm mo of of: f: Mouse clicks Escape followed by another character Control and another character The F1 through F12 function keys Alt and another character • • • • • 4. Wh hiss ssh do Wha hat at d do doe oe oes ess tthis she hel ellll ssc scr cri rip ipt p ptt d do? o? 5. FOO=/tmp/foo 6. if [ ! –d $FOO ]; then 7. mkdir $FOO fi • • • • • Creates /tmp/foo if it does not exist Outputs a message to the screen Creates /tmp/foo and raises an error if there is a problem Nothing, since there is a problem with the conditions in the if statement Makes the /tmp/foo directory if a file by that name exists 88 n are ab o e llo 8. Wh Whi h hiich iccch ho off tthe th h he e ffol oll llo low owi wing arrre ccor co orr rre rec ect cctt a bou bo out utt forr a an n nd dw wh whi h hil iille loo oop ops ps? ss? a (c h ttwo (cho ch hoo oos ose se tw w wo o)) • • • • • for loops have a test each cycle to determine if it should run again for loops operate over a fixed list of items for loops require a variable over which to iterate while loops operate over a fixed list of items while loops have a test each cycle to determine if it should run again 99 e he ffol pa 9. Gi Giv iiv ven en n tth he oll llowi ll win ing ing p par art rt o off a ssccri rip ipt pt: t: rri 10. if [ -f $1 ]; then 11. echo “I am here” 12. fi Wh h Wha hat att iiss tthe th he em mean ea anin aniing n ng go $1 $1? 1? me off $ • • • • It is a parameter to -f, indicating the size of the file It is the first argument passed to the script It is a special variable that indicates the exit code of the command before it It is a file called $1 • It is a list of files that gets interpolated 13. Given the foll following owing script that is rrun un through ./test.sh hello goodbye: 14. if [ -f $2 ]; then 15. echo "I am here" 16. fi When will “I am here” be printed? • • • • • If a file called “goodbye” exists in the current directory Never The script will always print “I am here” If there are two files in the current directory If a file called “hello” exists in the current directory 17. What is the correct way to a assign ssign the word “Hello” to a variable? • • • • • A = “Hello” echo “Hello” > A echo $A “Hello” $A=”Hello” A=”Hello” 18. What is the correct way to save the current directory to a variable? • • • • • A=`pwd` pwd | $A A=cwd A=pwd pwd $A 19. Which shell command accepts input fr from om the user’s keyboard? • • • • • 20. • • • • • 21. • • • • • echo read gets input $1 What informat information ion is held inside $? ? The name of the command run The previous command’s exit code The number of arguments passed to the script The current process id The current user ID How would you finish your script with an exit code of 42? return 42 break 42 CODE=42 exit 42 $?=42 22. The if command looks for what exit code to consider a condition to be true? • 1 • • • • 0 2 10 255 23. The number of users logged in is in a var variable iable called USERS. How would you test to see if 5 users are logged in? • • • • • test $USERS –eq 5 test –f USERS=5 test $USERS = 5 test $USERS,5 test $USERS –a 5 24. Given the foll following owing script: 25. while [ ! –f /tmp/foo ]; do 26. echo –n “.” 27. process_data > /tmp/foo 28. done Which of the following are true? (choose two) • • • • • The screen will fill with dots. If a file called /tmp/foo exists, process_data won’t be run process_data will be called at most once process_data will never be run /tmp/foo will be removed if it exists 29. A conditional that lets you make multiple comparisons with a pattern is called: • • • • • 30. • • • • • fanout case if branch test What is the meaning of $(( $i + 1)) ? 1 will be added to the i variable If i is 0, the loop will stop This will return the value of the next argument to the script This will return the value of the first argument to the script This runs the command stored in variable i 31. How would you writ write e a tes testt that says “if /tmp/ /tmp/foo foo is a directory or USERS is greater than 5”? • • • • test –d /tmp/foo –o $USERS –gt 5 test –d /tmp/foo | $USERS > 5 test /tmp/foo || $USERS > 5 test /tmp/foo –d –o $USERS -gt 5