The behavior of the grep command has changed with regards to searching for upper and lower case strings. Using interval searching in the [a-z] format is dependent on the LC_COLLATE variable.

You can set LC_COLLATE=C to preserve old behavior and to achieve proper results when performing interval searching with this method; however, in Red Hat Enterprise Linux 6, the recommended way of interval searching is to use the [[:lower:]],[[:upper:]] format.

This change can significantly affect output, so scripts and processes should be reviewed to continue to achieve the correct results.