Mastering Linux Shell Scripting

Which command is used to list all files and directories in the current directory in Linux?

• `ls`

• `cd`

• `pwd`

• `rm`

In a shell script, how do you assign the value "Hello" to a variable named `greeting`?

• `greeting = Hello`

• `greeting: Hello`

• `greeting="Hello"`

• `greeting <- Hello`

What is the purpose of the `if` statement in a shell script?

• To repeat a block of code multiple times

• To execute a block of code based on a condition

• To define a function

• To redirect input and output

Which command is used to redirect the output of a command to a file, overwriting the file if it exists?

• `command > file`

• `command >> file`

• `command < file`

• `command | file`

What is the significance of the `$?` variable in shell scripting?

• It stores the last executed command.

• It stores the exit status of the last executed command.

• It stores the current process ID.

• It stores the number of arguments passed to the script.

How would you use a `for` loop in a shell script to iterate over a list of files?

• `for file in ls; do echo $file; done`

• `for file in ls; echo $file; done`

Explain how you would handle errors in a shell script using `trap`.

• Use `trap` to execute a command when a signal is received.

• Use `trap` to ignore all errors in the script.

• Use `trap` to log errors to a file.

• Use `trap` to automatically retry failed commands.

Describe a scenario where input redirection would be useful in a shell script.

• When you want to save command output to a file.

• When you want to read input from a file instead of the keyboard.

• When you want to execute multiple commands in sequence.

• When you want to terminate a script early.

How can you check if a file exists in a shell script and print a message if it does?

• `if [ -f "file.txt" ]; then echo "File exists"; fi`

• `if [ -d "file.txt" ]; then echo "File exists"; fi`

• `if [ -e "file.txt" ]; then echo "File exists"; fi`

• `if [ -s "file.txt" ]; then echo "File exists"; fi`

Plan a shell script that takes a filename as an argument and counts the number of lines in the file. What command would you use?

• `wc -l $1`

• `cat $1 | wc -l`

• `grep -c $1`

• `awk '{print NR}' $1`