| | 1 | = Design differences from Unix and POSIX systems = |
| | 2 | |
| | 3 | == No `fork()`, no `exec()` == |
| | 4 | |
| | 5 | In traditional Unix, new processes are created by duplicating the resources of the current process via a call to `fork()`. Forking a process will, among other things, clone the current thread of that process. After `fork()`, both threads typically test whether they are the parent or the child instance. Very often, the child thread makes a call to `exec()` to load a new program. Calling `exec()` replaces the contents of the address space of the entire process with the new content of the loaded program. As can be seen, especially without heavy optimizations such as copy-on-write allocation of memory pages and non-duplicating variants of `fork()` such as `vfork()`, the procedure of spawning a new program is quite wasteful. |
| | 6 | |
| | 7 | In HelenOS, there is no `fork()` or `exec()` or any variant thereof. Programs are simply spawned by calling `task_spawn()`, which creates a separate new task for the loaded program and allows the caller to continue to run. Likewise, new threads and thread-like entities are created by calling `thread_create()` and `fibril_create()`. |
| | 8 | |
| | 9 | == No signals == |
| | 10 | |
| | 11 | To Be Written. |
| | 12 | |
| | 13 | == Lexical dot-dot resolution == |
| | 14 | |
| | 15 | To Be Written. |
