Linux Essentials 2.21 - Basic Scripting M11 Exam

A file begins with #!/bin/csh. This means:

• Nothing, this is a comment

• Running the script will invoke /bin/csh to interpret the rest of the file

• The operator should not be using /bin/csh

• This is a Perl script

• C Shell compatibility mode is enabled

Answer explanation

The line #!/bin/csh is a shebang that indicates the script should be run using the C shell located at /bin/csh. This means 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

Answer explanation

The appropriate editors for writing shell scripts are 'vi' and 'nano'. Both are text editors commonly used in Unix-like systems, while Firefox and LibreOffice Writer are not suitable for scripting.

Most of nano’s commands take the form of:

• Control and another character

• Alt and another character

• Mouse clicks

• Escape followed by another character

• The F1 through F12 function keys

Answer explanation

Most of nano's commands are executed using the Control key combined with another character, making 'Control and another character' the correct choice. This is a common shortcut method in many text editors.

What does this shell script do? bash CopyEdit FOO=/tmp/foo if [ ! -d $FOO ]; then mkdir $FOO fi

• Deletes the directory /tmp/foo if it exists

• Creates the directory /tmp/foo if it does not exist

• Renames /tmp/foo to /tmp/bar

• Lists the contents of /tmp/foo

Answer explanation

The script checks if the directory /tmp/foo does not exist. If it doesn't, it creates the directory. Therefore, the correct answer is that it creates the directory /tmp/foo if it does not exist.

Which of the following are correct about for and while loops? (Choose two)

• while loops have a test each cycle to determine if it should run again

• for loops have a test each cycle to determine if it should run again

• while loops operate over a fixed list of items

• for loops require a variable over which to iterate

• for loops operate over a fixed list of items

Answer explanation

While loops check a condition each cycle to decide if they should continue running. For loops typically iterate over a fixed list of items, making them suitable for such operations.

Given the following part of a script: bash copyEdit if [ -f $1 ]; then echo "I am here" fi What is the meaning of $1?

• It is a list of files that gets interpolated

• It is a file called $1

• It is a special variable that indicates the exit code of the command before it

• It is a parameter to -f, indicating the size of the file

• It is the first argument passed to the script

Answer explanation

In bash scripts, $1 refers to the first argument passed to the script when it is executed. This is why the correct answer is 'It is the first argument passed to the script'. The other options do not accurately describe $1.

When will “I am here” be printed?

• The script will always print “I am here”

• If a file called “goodbye” exists in the current directory

• Never

• If there are two files in the current directory

• If a file called “hello” exists in the current directory

Answer explanation

The script prints 'I am here' only if a file named 'goodbye' exists in the current directory. This condition is explicitly stated, making it the correct choice.

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”

Answer explanation

The correct way to assign the word 'Hello' to a variable is A="Hello". This syntax correctly assigns the string to the variable A. Other options either use incorrect syntax or do not perform an assignment.

What is the correct way to save the current directory to a variable?

• A=cwd

• pwd $A

• pwd | $A

• A=pwd

• A=pwd

Answer explanation

The correct way to save the current directory to a variable is by using 'A=pwd'. This assigns the output of the 'pwd' command, which prints the current working directory, to the variable A.

Which shell command accepts input from the user’s keyboard?

• $1

• echo

• read

• gets

• input

Answer explanation

The 'read' command is used in shell scripting to accept input from the user's keyboard, allowing the user to enter data that can be stored in a variable. Other options do not serve this purpose.