Shell scripting · Lesson 7 of 31 · 8 minutes

Awk reports

Build a small report from fields.

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Your objectives

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1
Capture auth process fields
Run awk '{print $5}' /var/log/auth.log | tee lab/auth-processes.txt.
Hint & worked example
Extract whitespace-delimited fields with the supported print patterns. Copy a stream both to a file and standard output; -a appends.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
awk '{print $5}' /var/log/auth.log | tee lab/auth-processes.txt
```
Remember: Quote awk programs so shell variable expansion does not consume $1; single quotes are usually appropriate. tee can overwrite a file even though the output is also visible on screen.
2
Read report
Run cat lab/auth-processes.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 lab/auth-processes.txt
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
3
Count report
Run wc -l lab/auth-processes.txt.
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 lab/auth-processes.txt
```
Remember: Text without a final newline may have fewer counted lines than visible rows.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

awk: Extract whitespace-delimited fields with the supported print patterns.
Quote awk programs so shell variable expansion does not consume $1; single quotes are usually appropriate.
tee: Copy a stream both to a file and standard output; -a appends.
tee can overwrite a file even though the output is also visible on screen.
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.
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

$ awk '{print $5}' /var/log/auth.log | tee lab/auth-processes.txt

sshd[104]:
sshd[118]:
sudo[126]:
sshd[141]:

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

$ cat lab/auth-processes.txt

sshd[104]:
sshd[118]:
sudo[126]:
sshd[141]:

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

$ wc -l lab/auth-processes.txt

4 lab/auth-processes.txt

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 “Awk reports”, 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 “Awk reports” 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.

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