if (! fork ())
exec (...);
It means that as soon as a child is forked, the next step is to replace its address space with that of the executable in exec(). So the step of actually copying the address spaces of parent into child is useless and uneccessary overhead, this extra copying is prevented in the call vfork().
Hence fork() can be used where vfork() is used, with an overhead, but simply calling vfork() without an exec is useless.
Ketan
Javier Guerra wrote:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 MAASK Group wrote:Vfork is a combination of fork() and exec().I am confused. The programmer explicitly has to call exec() after a vfork(). right?right, vfork() isn't a combination of fork() and exec(), more exactly, it's a version of fork() to be used only when immediatly followed by a exec() so, instead of writing if (! fork ()) exec (...); you could write if (! vfork ()) exec (...); and avoid the copying of the process segment that would be overwritten by exec(). in modern OSs, the process is marked copy-on-write, so it's just as fast, without the restrictions. that's why it's man page tells you not to use it anymore. - ------ Javier -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQE+Rn3HsIoGnxsRK/ERAmzmAJ0YLEju/TRGLnX8asM3vEN/MgMVXQCgpdUL B4WhKo2sgxVbxDkGq/QPbLo= =Bxlb -----END PGP SIGNATURE----- -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
-- Marriage is the triumph of imagination over intelligence. Second marriage is the triumph of hope over experience. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
