Chaining Unix Commands

Say, you want to execute a command only if another command is successful then you use &&.

And if you want a command to be executed if another command has failed, you use ||.

Create a file tea_ready:
```
touch tea_ready
```
The following command would print "Tea is ready" if tea_ready file exists:
```
ls -l tea_ready && echo "Tea is ready"
```
Delete the file tea_ready:
```
rm tea_ready
```
Check the command from #2 again:
```
ls -l tea_ready && echo "Tea is ready"
```

The following will print "Tea is not ready":

ls -l tea_ready || echo "Tea is not ready"

You can use brackets to avoid confusion:

(ls -l tea_ready && echo "Tea is ready") || echo "Tea is not ready"

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