Bash Shell Scripting - Command Substitution

The video tutorial explains command substitution in Linux, a feature that allows replacing a command with its output. It covers two methods: using backticks and the $() syntax. The tutorial demonstrates how to assign command outputs to variables and use them in shell scripts, with practical examples like extracting IP addresses and counting user sessions. The video concludes with a summary of the techniques discussed.

What is the primary purpose of command substitution in Linux?

• To replace a command with its output

• To execute multiple commands simultaneously

• To create a new shell environment

• To change file permissions

Which symbol is traditionally used for command substitution in Linux?

• Curly braces {}

• Backticks ``

• Square brackets []

• Parentheses ()

In the example provided, what command is used to capture the computer's hostname?

• uname

• whoami

• pwd

• hostname

What command is used to filter out IPv6 information in the example?

• sed 's/INET6//g'

• awk '{print $2}'

• cut -d' ' -f2

• grep -v INET6

Which command is used to extract only the IP addresses from the output?

• grep 'IP'

• awk '{print $2}'

• cut -d' ' -f1

• sed 's/IP//g'

What is the alternative syntax for command substitution introduced in the video?

• {command}

• $(command)

• [command]

How does the $(...) syntax differ from backticks in terms of execution?

• It runs the command in a subshell

• It executes the command in the background

• It requires root privileges

• It only works with single-line outputs

What command is used to count the number of user sessions in the example?

• who | wc -l

• uptime

• ps aux | grep user

• netstat -an | grep ESTABLISHED

Which command is used to display the users connected to the system?

• last

• finger

• users

• who

What is a key advantage of using command substitution directly in echo statements?

• It simplifies error handling

• It reduces memory usage

• It increases script execution speed

• It allows dynamic content generation