I totally agree.. I had just taken for granted that replacing a syscall would just mean changin its implementation keeping the behaviour constant. What if I want to extend an existing functionality? Most cliched example : compression and decomperssion of file data. So hook the read and write syscalls and in the hooked methods write the code for decompression and compression respectively.. Whats your take on that gurus? Thanks in advance -Shri -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/