lazy read

lazy_read.c

#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

ssize_t read (int __fd, void *__buf, size_t __nbytes) __wur
{

	static ssize_t (*orig_read)(int, void *, size_t)=NULL;

	if(orig_read==NULL)
	{
		orig_read = dlsym (RTLD_NEXT, "read");

		char * error;
		if ((error = dlerror()) != NULL)
		{
			fprintf (stderr, "lazy_read: %s\n", error);
			exit (EXIT_FAILURE);
		}

	}

	size_t ret = (*orig_read)(__fd, __buf, __nbytes);

	if(ret==0)
	{
		//TODO fuser /proc/*/fd/* /proc/*/fdinfo/*
		usleep(1000000);
		ret = (*orig_read)(__fd, __buf, __nbytes);
	}

	return ret;

}

gcc -Wall -fPIC -D_GNU_SOURCE -shared -o lazy_read.so lazy_read.c -ldl