Command-Line Interface Flashcards

Which command displays the current user's username in macOS Terminal?

Answer: whoami

The `whoami` command prints the effective username of the currently logged-in user.

A technician wants to view only the last 20 lines of a large log file. Which command achieves this?

Answer: tail -n 20 logfile.log

`tail -n 20` outputs the last 20 lines of the specified file.

Which command would you use to change the ownership of a file to a different user in macOS?

Answer: chown newuser filename

`chown` (change owner) sets the user and/or group ownership of a file.

What does the `&&` operator do when used between two shell commands?

Answer: Runs the second command only if the first succeeds

`&&` is a logical AND; the second command executes only when the first exits with status 0 (success).

Which `find` command locates all `.log` files modified within the last 7 days under `/var/log`?

Answer: find /var/log -name '*.log' -mtime -7

`find` with `-mtime -7` matches files modified less than 7 days ago.

A user runs `sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder`. What is the purpose of this command sequence?

Answer: Flush the DNS cache on macOS

This two-command sequence flushes the DNS cache and restarts mDNSResponder to apply the change on modern macOS.

Which command can be used to compress a folder named `reports` into a gzip-compressed tar archive called `reports.tar.gz`?

Answer: tar -czf reports.tar.gz reports

`tar -czf` creates (`c`) a gzip-compressed (`z`) archive file (`f`) from the specified directory.