Actually, maybe not full-blown Lex/Yacc. I\'m implementing a command-interpreter front-end to administer a webapp. I\'m looking for something that\'ll take a grammar definit
I'm not sure Lex/Yacc will be of any help. You'll just need a basic tokenizer and an interpreter which are faster to write by hand. If you're still into parsing route see Irony.
As a sidenote: have you considered PowerShell and its commandlets?