Codepad is a pastebin that runs your code for you. It was written by Steven Hazel. Codepad works like a compiler or interpreter, not like the read-eval-print loop of an interactive interpreter prompt. If you want to print the value of an expression, you need to use your language’s print command. If your language requires a “main” function, your program won’t work in codepad without one.
Steven has added support for many languages, including PHP, Python, Ruby and Perl.
How it works
Code execution is handled by a supervisor based on geordi. The strategy is to run everything under ptrace, with many system calls disallowed or ignored. Compilers and final executables are both executed in a chroot jail, with strict resource limits. The supervisor is written in Haskell.
“Hello World” examples: http://codepad.org/hello-world