Files and paths · Lesson 32 of 36 · 8 minutes

Sorted inventory comparison

Compare two sorted account inventories without modifying either file.

Open the lab Course map

Mastery 0/3Run itExplain itApply it

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 the first inventory
Run cat data/users-a.txt.
Hint & worked example
Read one or more files to standard output without editing their contents.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
cat data/users-a.txt
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
2
Read the second inventory
Run cat data/users-b.txt.
Hint & worked example
Read one or more files to standard output without editing their contents.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
cat data/users-b.txt
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
3
Compare the inventories
Run comm data/users-a.txt data/users-b.txt.
Hint & worked example
Compare sorted line sets and select unique or common columns.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
comm data/users-a.txt data/users-b.txt
```
Remember: Both inputs must be sorted under the same ordering rules.

Understand the pattern

Comparing sorted inventories with comm helps operators explain what they know before they change anything.

cat: Read one or more files to standard output without editing their contents.
Reading a source file should precede changing it; avoid printing real secrets.
comm: Compare sorted line sets and select unique or common columns.
Both inputs must be sorted under the same ordering rules.

Worked example and expected result

$ cat data/users-a.txt

admin
learner
www-data

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

$ cat data/users-b.txt

backup
learner
www-data

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

$ comm data/users-a.txt data/users-b.txt

admin
	backup
		learner
		www-data

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 “Sorted inventory comparison”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.Reading a source file should precede changing it; avoid printing real secrets.

Apply it elsewhere

Before adapting the cat workflow from “Sorted inventory comparison” 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: Restore copy verification Try an incident drill

Anonymous lesson and mastery progress lasts for this session. Sign in to keep synced lesson XP between sessions; mastery stays device-local. No speed bonus, lost lives, or hint penalties.

Keep learning

GNU Coreutils manual · GNU Bash manual