010-160 - LPI Linux Essentials Basic Scripting Concepts Questions and Answers

Question 1

A shell script contains the following lines:

MY_VAR="Linux System"
echo "I am learning about the '$MY_VAR'"
echo "I am learning about the \"$MY_VAR\""

What is the output when this script is executed?

Accepted Answer

I am learning about the '$MY_VAR'
I am learning about the "Linux System"

Answer

Single quotes (') prevent any kind of expansion, so '$MY_VAR' is printed literally. Double quotes (") allow for variable expansion, so "$MY_VAR" is replaced with its value, "Linux System". The backslashes before the inner double quotes are necessary to escape them so they are printed as literal characters.

Question 2

Which of the following lines in a script correctly executes the `whoami` command and assigns its output to a variable named `CURRENT_USER`?

Accepted Answer

CURRENT_USER=$(whoami)

Answer

The `$(command)` syntax is used for command substitution. It executes the command within the parentheses (`whoami`) and substitutes its standard output. This output is then assigned to the `CURRENT_USER` variable.

Question 3

What is the primary purpose of the `#!/bin/bash` line at the beginning of a shell script?

Accepted Answer

It specifies the absolute path to the interpreter that should execute the script.

Answer

This line, known as a 'shebang', is an interpreter directive. It tells the operating system's program loader which program (in this case, `/bin/bash`) should be used to run the commands contained in the script.

Question 4

A user creates a script named `greet.sh` with the content `echo "Hello, $1"`. How should the user execute this script to produce the output `Hello, David`?

Accepted Answer

./greet.sh David

Answer

Arguments passed to a script on the command line are known as positional parameters. `$1` refers to the first argument, `$2` to the second, and so on. By running `./greet.sh David`, the string "David" becomes the first argument and is substituted for `$1` within the script.

Question 5

After a command fails in a shell script, what is the most reliable way to check for this failure condition?

Accepted Answer

Check if the output of the `$?` variable is a non-zero value.

Answer

The special shell variable `$?` always holds the exit status of the most recently executed foreground command. By convention, an exit status of 0 indicates success, while any non-zero value indicates an error or failure.

(010-160) LPI Linux Essentials Practice Test

(010-160) LPI Linux Essentials Practice Test

010-160 - LPI Linux Essentials Basic Scripting Concepts Questions and Answers