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Is there any equivalent in Windows to Unix Shell's "exec"? Basically, I need to avoid forking a new process, so that input/output pipes are preserved, as well as process id.

Edit:

So, here's my problem. I have a process A that starts a script, and this script ends by executing a process B. I need for A to get all of B's output, as well as be able to kill B by killing the process it has spawned (the script).

On Unix, executing B with exec does that job.

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There is no equivalent, at least not using standard Windows commands and programs. –  John Gardeniers Sep 24 '11 at 8:47
    
If you're trying to run an executable, rather than another batch file, there is no (supported/realistic) way of doing this. However, input/output pipes are normally inherited by applications running in a batch file. If you can describe why you want to do this, we may be able to suggest alternatives. –  Harry Johnston Sep 25 '11 at 20:41
    
Process A should already get all of B's output, unless the script overrides this. Is this not working? –  Harry Johnston Sep 26 '11 at 2:17
    
It is possible using the Win32 API to arrange for a child process to die when the parent process does, however there is no built-in command-line option AFAIK. If I provide some source code (for Visual C++) are you able to build it? –  Harry Johnston Sep 26 '11 at 2:26
    
@Harry I'm forking the script from Java, so, if the idea is for process A to use that Win32 API, I'm afraid that's unlikely to work, though I'm thankful for the effort. Better just to explain it isn't possible, and I'll accept that as the answer. –  Daniel C. Sobral Sep 26 '11 at 13:15

2 Answers 2

AFAIK there isn't. Windows lacks execv() which is how bash exec does it. call works for calling batch files (easy, just interpret the file in the current interpreter, similar to bash's . command) but not for exes.

This makes it impossible to write one-liner wrapper scripts for scripts in any language on Windows. You'll always get that "Terminate batch job?" crap on Ctrl+C and killing the batch process (not with Ctrl+C, from task manager say) won't kill the child process. I'm now looking for a C template file to do this wrapping.

UPDATE: Windows does have _execv() in its POSIX compatibility layer in MSVCRT, but AFAIK (haven't tested it) it's just a wrapper around CreateProcess so it will always create a new process, it cannot replace the current process.

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I think call does what you want, but I'm not 100% sure.

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3  
If you want to run one batch file from another, without launching a new instance of cmd.exe, call is the right answer. –  Harry Johnston Sep 25 '11 at 20:39

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