Terminal basics · Lesson 26 of 34 · 8 minutes

Option reading drill

Use help output before applying search options to a log.

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learner@clairos:~ $

↑ history · Tab complete · Ctrl+C cancel · Esc, Tab to leaveExit 0

Your objectives

Hints are always available. Wrong turns never cost XP.

1
Read grep options
Run man grep.
Hint & worked example
Read a short built-in teaching reference for one supported command.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
man grep
```
Remember: For real administration, check the installed command manual and version too.
2
Apply a literal search
Run grep denied /var/log/auth.log.
Hint & worked example
Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
grep denied /var/log/auth.log
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
3
Review the sequence
Run history.
Hint & worked example
Review commands entered during this session. History is a navigation aid, not evidence that a command succeeded.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
history
```
Remember: Completion in this release checks command outcomes, not history strings alone.

Understand the pattern

Checking command options before using them helps operators explain what they know before they change anything.

man: Read a short built-in teaching reference for one supported command.
For real administration, check the installed command manual and version too.
grep: Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
No matches is exit status 1, which is different from a malformed invocation.
history: Review commands entered during this session. History is a navigation aid, not evidence that a command succeeded.
Completion in this release checks command outcomes, not history strings alone.

Worked example and expected result

$ man grep

GREP(1)
NAME
  grep - search simulated text
SYNOPSIS
  grep [-i] <text> <file>
NOTE
  Pipes are limited to safe text commands.

Exit status: 0. The command completed successfully in the training fixture.

$ grep denied /var/log/auth.log

May 26 08:18:33 clairos-learn sshd[118]: denied password for root
May 26 08:21:44 clairos-learn sshd[141]: denied password for admin

Exit status: 0. The command completed successfully in the training fixture.

$ history

   1  man grep
   2  grep denied /var/log/auth.log

Exit status: 0. The command completed successfully in the training fixture.

Try a variation

Repeat this workflow in the sandbox with a different scratch filename. Keep the system fixtures unchanged and compare the observed output with your expectation before moving on.

Explain it

In “Option reading drill”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.No matches is exit status 1, which is different from a malformed invocation.

Apply it elsewhere

Before adapting the grep workflow from “Option reading drill” to another server, what should you do?Skip output inspection whenever the command is familiar.Confirm the current directory, target identity, permissions, and the installed command behavior first.Paste the training paths unchanged into production.

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Quoted paths with spaces Try an incident drill

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