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