Chapter 11 Exam Flashcards
A file begins with #!/bin/csh. This means:
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
Running the script will invoke /bin/csh to interpret the rest of the file
Which are appropriate editors for writing shell scripts?
(choose two)
Firefox /bin/bash LibreOffice Writer vi nano
vi
nano
Most of nano’s commands take the form of:
Mouse clicks Escape followed by another character Control and another character The F1 through F12 function keys Alt and another character
Control and another character
What does this shell script do?
FOO=/tmp/foo
if [ ! –d $FOO ]; then
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
Creates /tmp/foo if it does not exist
Which of the following are correct about for and while loops?
(choose two)
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
for loops operate over a fixed list of items
while loops have a test each cycle to determine if it should run again
Given the following part of a script:
if [ -f $1 ]; then
echo “I am here”
fi
What is the meaning of $1?
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
It is the first argument passed to the script
Given the following script that is run through ./test.sh hello goodbye:
if [ -f $2 ]; then
echo “I am here”
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
If a file called “goodbye” exists in the current directory
What is the correct way to assign the word “Hello” to a variable?
A = “Hello” echo “Hello” > A echo $A “Hello” $A=”Hello” A=”Hello”
A=”Hello”
What is the correct way to save the current directory to a variable?
A=`pwd` pwd | $A A=cwd A=pwd pwd $A
A=pwd
Which shell command accepts input from the user’s keyboard?
echo read gets input $1
read
What information 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
The previous command’s exit code
How would you finish your script with an exit code of 42?
return 42 break 42 CODE=42 exit 42 $?=42
exit 42
The if command looks for what exit code to consider a condition to be true?
1 0 2 10 255
0
The number of users logged in is in a variable 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
test $USERS –eq 5
Given the following script:
while [ ! –f /tmp/foo ]; do
echo –n “.”
process_data > /tmp/foo
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
If a file called /tmp/foo exists, process_data won’t be run
process_data will be called at most once
