Collection of useful bash functions.

Every script file includes the function and a test to show how it's meant to be used and check that the function really works. Just executing the script runs that test.

## Check folder for extension

Checks a given folder for certain file extensions recursively. All found files with the extension(s) are returned in a global array; New files are appended to the array.

The [check_folder_for_extension test folder](cffe_test) contains of 13 files, 12 of them images, which should be found by the test.

function call:
```
check_folder ./cffe_test "*.jpg *.JPG"
```
For multiple extensions (or other parts of the file name to match) space separate the list, like shown above.


## Clean up

Cleaning up in a script and exit with a given exit code.

function call:
```
clean_up 0;
```

For testing the function call the script with:
```
clean_up.sh test
```

## Logger

[Logger](logger.sh) to write messages with individual levels to a file. 

In level *debug* all logged messages are printed to stdout, too.

Log levels are 

5 LLDebug,     *for exceptionally verbose messages, also on std out*

4 LLInfo,      *informative messages*

3 LLWarning,   *warning messages*

2 LLError,     *error messages*

1 LLMdtry and  *mandatory messages to get minimal info in a log file*

0 LLMute       *really nothing gets written*

The higher the level set in `$Log_Level` to the logger, the more verbose it gets.

```
logger $LLWARNING "This is my message";
```
produces the following message in the log file:

```
logger 20231122_22:43:19 Warning: This is my message!
```
