Linux Command Line & Shell Scripting Flashcards

Which shell built-in command displays the value of a variable named MYVAR?

Answer: echo $MYVAR

The echo command followed by the variable name prefixed with $ displays its value.

What does the pipe operator | do in a shell command?

Answer: Sends the output of one command as input to another

The pipe | connects the stdout of the left command to the stdin of the right command.

Which command lists only the directories inside /home?

Answer: ls -d /home/*/

ls -d /home/*/ matches only directory entries by appending a trailing slash glob.

In a bash script, what does the special variable $? represent?

Answer: The exit status of the last command

$? holds the exit code returned by the most recently executed foreground command.

Which command would you use to search for the string 'error' in all .log files under /var/log?

Answer: grep -r 'error' /var/log/*.log

grep with a pattern and a file glob searches for matching text within the specified files.

What is the result of running: echo {a,b,c}.txt?

Answer: Prints: a.txt b.txt c.txt

Brace expansion generates the strings a.txt, b.txt, and c.txt, which echo then prints.

Which redirection operator appends standard output to an existing file without overwriting it?

Answer: >>

The >> operator opens the file in append mode, adding new output after existing content.