Text and logs · Lesson 18 of 38 · 8 minutes

Cut field selection

Extract colon-delimited identity fields.

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
Extract names
Run cut -d : -f 1 /etc/passwd.
Hint & worked example
Extract delimiter-separated fields or character ranges from text.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
cut -d : -f 1 /etc/passwd
```
Remember: A delimiter parser is not a general CSV parser with quoted fields.
2
Extract ids
Run cut -d : -f 3 /etc/passwd.
Hint & worked example
Extract delimiter-separated fields or character ranges from text.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
cut -d : -f 3 /etc/passwd
```
Remember: A delimiter parser is not a general CSV parser with quoted fields.
3
Read source
Run cat /etc/passwd.
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 /etc/passwd
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

cut: Extract delimiter-separated fields or character ranges from text.
A delimiter parser is not a general CSV parser with quoted fields.
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.

Worked example and expected result

$ cut -d : -f 1 /etc/passwd

root
learner
www-data

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

$ cut -d : -f 3 /etc/passwd

0
1000
33

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

$ cat /etc/passwd

root:x:0:0:root:/root:/bin/bash
learner:x:1000:1000:Clairos Learner:/home/learner:/bin/fake-sh
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin

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 “Cut field selection”, which interpretation is safe?A successful first check guarantees that every dependent service is healthy.A delimiter parser is not a general CSV parser with quoted fields.A command appearing in history proves it completed successfully.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Text case transforms 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