What is the purpose of the touch command?

Linux operating system is:

What is the purpose of the makewhatis command?

What does permission 777 denote?

Which of the following commands lets you search for text in a file without opening the file first?

What does the head command do?

To verify what state (run level) you are currently running in, you use:

How to find out memory usage:

Using cat command, which option is used to print the line number?

What does the 'tcpdump' command do?

what does the following command do? 'watch -n 1 du -hs /tmp/file'