Linux+ Bash Scripting and Automation Flashcards

What does the 'xargs' command primarily do in a pipeline?

Answer: Builds and executes commands using arguments read from stdin

xargs reads items from stdin and passes them as arguments to a specified command, enabling mass operations like xargs rm.

A Bash array is declared as arr=(a b c). What does echo ${arr[@]} output?

Answer: a b c

${arr[@]} expands to all elements of the array as separate words, and echo joins them with spaces.

Which signal number does 'kill -9 PID' send to a process?

Answer: SIGKILL (9)

SIGKILL (signal 9) immediately terminates a process and cannot be caught, blocked, or ignored by the target process.

What is the purpose of the 'at' command in Linux automation?

Answer: Schedules a job to run at a specific future time once

The at command schedules a command or script to execute once at a specified future date and time, unlike cron which is recurring.

In Bash, what does 'declare -r myvar=5' do?

Answer: Declares myvar as a read-only integer variable

declare -r creates a read-only variable that cannot be modified or unset after declaration, similar to readonly.

Which command checks the syntax of a Bash script without executing it?

Answer: bash -n script.sh

bash -n reads the script and checks for syntax errors without executing any commands, useful for pre-validation.

What does the 'tee' command do when used in a pipeline?

Answer: Reads stdin and writes it to both stdout and a file simultaneously

tee reads from stdin and writes identical output to both stdout (for further piping) and one or more files at the same time.