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System calls vs. library functions

System calls vs. library functions

Posted Aug 20, 2008 20:06 UTC (Wed) by asamardzic (guest, #27161)
In reply to: System calls vs. library functions by johnkarp
Parent article: Standards, the kernel, and Postfix

POSIX (actualy SUS nowadays) describes "system interfaces", which are exposed as C functions, usually directly mapping to actual system calls. As the links behavior is tightly coupled with file system implementation, related code is usually part of the kernel, thus link() has not much to do in userspace, and this particular issue probably has to be resolved within the kernel code.


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System calls vs. library functions

Posted Aug 20, 2008 20:35 UTC (Wed) by nix (subscriber, #2304) [Link]

Pedant point: POSIX incorporated all of SuS some years back; the result is 
called POSIX. (Confusing, I know.)

System calls vs. library functions

Posted Aug 21, 2008 3:50 UTC (Thu) by mkerrisk (subscriber, #1978) [Link]

Pedant point: POSIX incorporated all of SuS some years back; the result is called POSIX. (Confusing, I know.)

Well, to be extrememly pedantic, the work of the Austin group consolidated earlier POSIX standards and SUSv2, to create a new standard that defines two levels of conformance: base conformance (aka POSIX.1-2001), and XSI (X/Open System Interface) conformance (aka SUSv3). So the result is called both POSIX and SUS.

System calls vs. library functions

Posted Aug 21, 2008 3:52 UTC (Thu) by mkerrisk (subscriber, #1978) [Link]

See also http://www.kernel.org/doc/man-pages/online/pages/man7/standards.7.html

System calls vs. library functions

Posted Aug 21, 2008 9:06 UTC (Thu) by nix (subscriber, #2304) [Link]

That manpage, and the posixoptions manpage it links to, are excellently done. (It is a tad
unclear, though, whether posixoptions describes the meaning of the options or whether it
instead describes what values those options have got on a Linux (glibc?) system...)


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