Text and logs · Lesson 13 of 38 · 7 minutes

Access log review

Filter training HTTP access lines for status and method clues.

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Your objectives

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1
Search 404
Run grep 404 /var/log/nginx-access.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 404 /var/log/nginx-access.log
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
2
Search POST
Run grep POST /var/log/nginx-access.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 POST /var/log/nginx-access.log
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
3
Count access log
Run wc -l /var/log/nginx-access.log.
Hint & worked example
Count input. -l counts newline characters, -w counts whitespace-delimited words, and -c counts bytes.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
wc -l /var/log/nginx-access.log
```
Remember: Text without a final newline may have fewer counted lines than visible rows.

Understand the pattern

Web operators use access logs to verify routing and probes.

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.
wc: Count input. -l counts newline characters, -w counts whitespace-delimited words, and -c counts bytes.
Text without a final newline may have fewer counted lines than visible rows.

Worked example and expected result

$ grep 404 /var/log/nginx-access.log

127.0.0.1 GET /api/test 404

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

$ grep POST /var/log/nginx-access.log

127.0.0.1 POST / 405

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

$ wc -l /var/log/nginx-access.log

3 /var/log/nginx-access.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 “Access log review”, 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 “Access log review” 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: Error patterns Try an incident drill

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