Shell scripting · Lesson 10 of 31 · 8 minutes

Tee script logs

Capture command output as a script log.

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learner@clairos:~ $

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Your objectives

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1
Capture log
Run printf script-log | tee lab/script.log.
Hint & worked example
Format data deliberately, including separators and final newlines. 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.
```
printf script-log | tee lab/script.log
```
Remember: A format string controls output; a newline is data, not an automatic guarantee. tee can overwrite a file even though the output is also visible on screen.
2
Read log
Run cat lab/script.log.
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/script.log
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
3
Inspect log
Run stat lab/script.log.
Hint & worked example
Inspect a file or directory metadata record, including ownership, permissions, and size.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
stat lab/script.log
```
Remember: Metadata and file contents answer different questions.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

printf: Format data deliberately, including separators and final newlines.
A format string controls output; a newline is data, not an automatic guarantee.
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.
stat: Inspect a file or directory metadata record, including ownership, permissions, and size.
Metadata and file contents answer different questions.

Worked example and expected result

$ printf script-log | tee lab/script.log

script-log

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

$ cat lab/script.log

script-log

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

$ stat lab/script.log

Path: /home/learner/lab/script.log
Type: file
Mode: -rw-r--r--
Owner: learner
Group: learners
Size: 10 bytes

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

Apply it elsewhere

Before adapting the cat workflow from “Tee script logs” 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.

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