I wrote a shell in C for Bruce Molay's Unix System Programming class. I thought the hardest part was getting the globbing, special characters, and escaping to work right. The other element of Unix system programming in C (that some may not be aware of) is that you are expected to make sure every line is 80 char or less. At the end of the day, I was proud of what I accomplished, but I think I only got a _C_ on the assignment.