Long ago in the far away land of UNIX, fork was a primitive because the primary use of fork was to do more work on the system. You likely were one of thee or four other people, at any given moment vying for CPU time, and it wasn't uncommon to see loads of 11 on a typical university UNIX system.
> so why is there not a fork-exec combo
you're looking for system(3). Turns out, most people waitpid(fork()). Windows explicitly handles this situation with CreateProcess[0] which does a way better job of it than POSIX does (which, IMO, is the standard for most of the win32 API, but that's a whole can of worms I won't get into).
> why would anyone ever use vfork?
Small shells, tools that need the scheduling weight of "another process" but not for long, etc. See also, waitpid(fork()).
When you have something with MASSIVE page tables, you don't want to spend the time copying the whole thing over. There's a huge overhead to that.
system(3) is not a good alternative because it indirects through the shell, which adds the overhead of launching the shell as well as the danger of misinterpreting shell metacharacters in the command if you aren’t meticulous about escaping them correctly.
Long ago in the far away land of UNIX, fork was a primitive because the primary use of fork was to do more work on the system. You likely were one of thee or four other people, at any given moment vying for CPU time, and it wasn't uncommon to see loads of 11 on a typical university UNIX system.
> so why is there not a fork-exec combo
you're looking for system(3). Turns out, most people waitpid(fork()). Windows explicitly handles this situation with CreateProcess[0] which does a way better job of it than POSIX does (which, IMO, is the standard for most of the win32 API, but that's a whole can of worms I won't get into).
> why would anyone ever use vfork?
Small shells, tools that need the scheduling weight of "another process" but not for long, etc. See also, waitpid(fork()).
When you have something with MASSIVE page tables, you don't want to spend the time copying the whole thing over. There's a huge overhead to that.
[0] https://docs.microsoft.com/en-us/windows/win32/api/processth...