5 exercises — pipes, daemons, stdin/stderr, file permissions, SSH — the command-line concepts that every backend and DevOps engineer uses daily.
0 / 10 completed
1 / 10
"Chain the commands with a pipe: cat access.log | grep ERROR | wc -l." What does the pipe operator | do here?
The pipe operator | connects the stdout of one process to the stdin of the next — in memory, without writing to disk. In cat access.log | grep ERROR | wc -l: cat reads the file → grep ERROR filters lines containing "ERROR" → wc -l counts them. Pipes are a core Unix philosophy: small tools that do one thing well, composable with pipes. Compare with redirect (>), which writes output to a file instead of another command.
2 / 10
"The nginx daemon is running in the background and listening on port 443." What is a daemon?
A daemon (pronounced "dee-mon") is a long-running background process detached from any terminal. Naming convention: daemons typically end in 'd' — sshd (SSH server), nginx, systemd, crond. They are managed with systemctl start/stop/status nginx on systemd systems. Unlike interactive processes, daemons log to syslog or their own log files and restart automatically on crash. A cron job differs — it's a scheduled process that runs for a short time and exits.
3 / 10
"The script exited with a non-zero code — check _____ to see the error messages." Which stream carries error output in Unix?
Unix processes have three standard streams: stdin (file descriptor 0) — input, usually the keyboard or a pipe; stdout (fd 1) — normal output, usually the terminal; stderr (fd 2) — error and diagnostic messages. Separating stdout and stderr lets you pipe only good output while still seeing errors: command 2>errors.log redirects stderr to a file. To redirect both: command >out.txt 2>&1. This is why CI logs often show application output separately from error traces.
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"Use chmod 755 to make the script executable." What do the three digits in 755 represent?
Unix file permissions use three octal digits representing owner / group / others. Each digit is the sum of: r=4 (read), w=2 (write), x=1 (execute). So 755 means: owner gets 7 (4+2+1 = rwx), group gets 5 (4+0+1 = r-x), others get 5 (r-x). This is typical for executables — the owner can read/write/execute; everyone else can only read and run it. 644 (rw-r--r--) is typical for regular files. View permissions with ls -la; change them with chmod; change owner with chown.
5 / 10
"I'll SSH into the box and check the logs." What does SSH stand for, and what does it provide?
SSH (Secure Shell) lets you log into a remote server and run commands as if you were sitting at its terminal — but the connection is fully encrypted. The standard port is 22. You authenticate with a password or, more securely, an SSH key pair (private key stays on your machine; public key goes on the server in ~/.ssh/authorized_keys). Common uses: ssh user@server for interactive sessions; scp file user@server:/path for file transfers; ssh -L 5432:localhost:5432 user@server for port forwarding (tunnelling a database connection). SSH replaced the insecure telnet and rsh.
6 / 10
A developer needs to quickly check the status of a database server. They run `ping dbserver.example.com` and receive replies with round trip times. What does the `ping` command primarily do?
The `ping` command is used to test network connectivity. It sends ICMP echo requests to the specified host and measures the time it takes for a response to return. This provides an indication of whether the server is reachable and how quickly data can travel—crucial for troubleshooting performance issues. Options A, C, and D describe other functions.
7 / 10
A system administrator needs to remotely access a server to troubleshoot an issue. They use the command `ssh user@server`. What does SSH stand for?
SSH stands for Secure Shell. It's a cryptographic network protocol used for operating network services over an unsecured network. It provides a secure channel for remote login and command execution. Options B, C, and D are incorrect descriptions of the technology.
8 / 10
A developer is reviewing code that uses the `grep` command: `grep -i 'error' logfile.txt`. What does the `-i` option in this command do?
The `-i` option in `grep` stands for 'ignore case'. It tells `grep` to perform a case-insensitive search. This means it will match 'error', 'Error', 'ERROR', etc., when searching for the specified pattern. Options B, C, and D describe different functionalities of the `grep` command.
9 / 10
A system administrator is setting permissions on a directory called 'secrets' using the `chmod` command. What does `chmod 755 secrets` mean?
The `chmod` command sets file permissions. The digits in '755' represent the permissions: 7 (read, write, execute) for the owner, 5 (read, execute) for the group, and 5 (read, execute) for others. This configuration is commonly used to protect sensitive files while still allowing authorized users to access them.
10 / 10
A developer needs to quickly share a snippet of code with another team member via Slack. They copy and paste the code directly into the chat window. What is the primary purpose of Slack in this context?
Slack is primarily a messaging platform designed for team communication. When a developer pastes code into Slack, they're leveraging its ability to share information quickly and facilitate discussions about that code in real-time. Options A, B, and C describe other functionalities or uses of the platform.
What does the "Linux & CLI Vocabulary" vocabulary exercise cover?
This exercise tests real IT vocabulary related to linux & cli vocabulary through 10 multiple-choice questions, each built from realistic workplace sentences rather than abstract definitions.
Is this vocabulary exercise free to use?
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How many questions does this exercise have?
This exercise has 10 questions. Each one shows a real-world sentence or scenario with multiple-choice options and an explanation once you answer.
What happens after I answer a question?
You'll see immediate feedback showing whether your answer was correct, along with a short explanation of why — then a button to move to the next question, and a full results screen at the end.
Can I retry the exercise if I get questions wrong?
Yes. Once you reach the results screen, click "Try again" to reset your answers and go through the exercise from the start as many times as you like.
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No account is needed. Your answers are scored in your browser during the session — nothing is saved to a server, so you can jump straight in.
Is my progress saved if I leave the page?
No — progress within an exercise resets if you navigate away or reload. Each exercise is short enough to complete in a few minutes in one sitting.
Are these vocabulary exercises connected to other topics?
Yes — this module shares real-world context with 1 other vocabulary module. See "Related vocabulary" below to keep building a connected skill set.
How is this different from reading a glossary or blog article?
Exercises like this one are active recall drills — you have to choose the correct term or phrasing yourself, which builds retention faster than passively reading a definition.
Where can I find more vocabulary exercises?
Browse the full Vocabulary exercises hub for hundreds of modules covering Agile, DevOps, security, databases, architecture, and more — organised by IT role and skill.