Text and logs · Lesson 32 of 38 · 8 minutes

Sorted account diff

Use comm to separate shared and unique account names.

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
Number the first set
Run nl data/users-a.txt.
Hint & worked example
Number input lines for a readable evidence reference.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
nl data/users-a.txt
```
Remember: Line numbers depend on the exact file version and numbering mode.
2
Number the second set
Run nl data/users-b.txt.
Hint & worked example
Number input lines for a readable evidence reference.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
nl data/users-b.txt
```
Remember: Line numbers depend on the exact file version and numbering mode.
3
Compare both sets
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

Explaining differences between sorted text sets helps operators explain what they know before they change anything.

nl: Number input lines for a readable evidence reference.
Line numbers depend on the exact file version and numbering mode.
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

$ nl data/users-a.txt

     1	admin
     2	learner
     3	www-data

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

$ nl data/users-b.txt

     1	backup
     2	learner
     3	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 account diff”, which interpretation is safe?Line numbers depend on the exact file version and numbering mode.A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Journal line numbering Try an incident drill

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