Shell scripting · Lesson 23 of 31 · 8 minutes

Executable bit review

Set executable mode only after reading a script.

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

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1
Read health script
Run cat scripts/health-check.sh.
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 scripts/health-check.sh
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
2
Set executable
Run chmod 755 scripts/health-check.sh.
Hint & worked example
Change permissions using an octal mode or a symbolic adjustment. Each rwx bit belongs to owner, group, or other.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
chmod 755 scripts/health-check.sh
```
Remember: Do not use 777 as a blanket fix. Grant the smallest access needed.
3
Inspect health script
Run stat scripts/health-check.sh.
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 scripts/health-check.sh
```
Remember: Metadata and file contents answer different questions.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

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.
chmod: Change permissions using an octal mode or a symbolic adjustment. Each rwx bit belongs to owner, group, or other.
Do not use 777 as a blanket fix. Grant the smallest access needed.
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

$ cat scripts/health-check.sh

#!/bin/sh
set -eu
systemctl status nginx
ss -tulpn

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

$ chmod 755 scripts/health-check.sh

(no output; exit 0)

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

$ stat scripts/health-check.sh

Path: /home/learner/scripts/health-check.sh
Type: file
Mode: -rwxr-xr-x
Owner: learner
Group: learners
Size: 50 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 “Executable bit review”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.Do not use 777 as a blanket fix. Grant the smallest access needed.

Apply it elsewhere

Before adapting the chmod workflow from “Executable bit review” 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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