How to tell if a file is open in C?

wwuster · 07-16-2009, 06:18 AM

I need a function in C that will tell me if a file is already open. I've been searching for such a thing but can't find one. This is for Ubuntu 9.04.

thanks,
William

PMP · 07-16-2009, 06:47 AM

man lsof

Hko · 07-16-2009, 11:58 AM

"lsof" is a program, not a C function call.

But there is no such function call. To make one, you would first need to get the full path of a given file ath. This can be done with the realpath (3) library function. Then scan all /proc/[0-9]*/fd/* and call readlink (2) on each symlink found and compare with the full path you got from calling realpath (3) in the first step. If there is a match the file is open.

This is (briefly) what the "lsof" and "fuser" programs do.