Exercise

Preventing Clobber Exercise

Task

Stop > from silently destroying a file you meant to keep, then make that protection permanent.

Hosts: workstation, then servera

Create a file holding data you care about

cd ~
echo "quarterly revenue: 4200" > finance_report.txt
cat finance_report.txt

Enable noclobber and try to overwrite it

set -o with no arguments lists every shell option and whether it is on.
```
set -o | grep noclobber
set -o noclobber
```
Now make the mistake noclobber exists to prevent. The redirect is refused and the file survives.
```
echo "oops, wrong file" > finance_report.txt
echo $?
cat finance_report.txt
```
Append, then overwrite on purpose

Appending is never destructive, so noclobber allows it.
```
echo "quarterly expenses: 3100" >> finance_report.txt
cat finance_report.txt
```
>| says you really do mean to overwrite. noclobber is a seatbelt, not a lock.
```
echo "superseded by the audited figures" >| finance_report.txt
cat finance_report.txt
```
Confirm the option is off again in a new session

Log out of servera and log back in.
```
exit
ssh servera
set -o | grep noclobber
```
Persist noclobber in ~/.bashrc
```
vim ~/.bashrc
```
```
set -o noclobber
```
```
exit
ssh servera
set -o | grep noclobber
echo "test" > finance_report.txt
```
Scripts do not inherit this ~/.bashrc is read by interactive shells. A script that needs noclobber has to set it for itself.

Clean up
```
rm finance_report.txt
```