A GREP developer largely works with the GREP (Global Regular Expression Print) command-line utility, a powerful tool used in text parsing and data refinement. Their primary role involves writing and debugging complex regular expressions to search, filter, or manipulate text within files. They may also automate tasks by integrating GREP into scripts or software programs. Additionally, a GREP developer might be responsible for teaching others how to use GREP effectively, creating comprehensive documentation, and optimizing the performance of GREP commands. They need to have a strong understanding of pattern matching and UNIX/Linux environments.