Comment by amluto
20 hours ago
Help me out here, please. Off the top of my head, the exec command is dependent on exec, except that a spawn + wait implementation would be a mostly okay substitute.
Pipes and redirections don’t need fork + exec. Neither do subshells.
If you use pipe() you get two ends in the same process, then you fork and child and parent can communicate. This is how a unix shell setups up pipes and it is rather elegant.
Doing the same thing on Windows, I create the pipe and get two ends in the same process. Then I'd call CreateProcess and indicate I want the pipe's handle (fd) inherited to the child, and I'd use a prearranged way to tell the child what the fd value is it should use.
Possibly the most common way to tell the child the value is by setting it as a CLI arg in CreateProcess.
Yes, and CreateProcess needs special facilities to make this possible while in the UNIX model you don't.