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What are the POSIX like functions in MSVC's C runtime?

Tags:

c

visual-studio

visual-c++

winapi

Today I stumbled to MSDN's documents about Visual C++'s C runtime (example: http://msdn.microsoft.com/en-us/library/8syseb29.aspx) and find to my surprise a lot of functions that look just like POSIX syscalls: dup2, fdopen, stat, execlp, ..., except being prefixed with _ or _w. Are these functions just wrappers to Windows API? Are they only usable with the POSIX subsystem? Are they deprecated/going to be deprecated?

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Siyuan Ren Avatar asked May 05 '14 16:05

Siyuan Ren

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1 Answers

These functions are wrappers around Win32 APIs. You don't need to have the POSIX subsystem to use them. They are not likely to disappear - Microsoft takes backwards compatibility very seriously.

You can find the source code of the MS CRT in "\Program Files (x86)\Microsoft Visual Studio X.0\VC\crt\src". E.g. you can see that _dup2 is calling DuplicateHandle and _stat is using FindFirstFileEx.

As for why they got the underscores, I could not find an official reason, but I suspect it's probably because these functions don't provide full POSIX compliance.

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Igor Skochinsky Avatar answered Sep 17 '22 00:09

Igor Skochinsky
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