hook_read.c

#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <dlfcn.h>

ssize_t read(int fd, void *buf, size_t count) {
    ssize_t (*origin_read)(int, void*, size_t) = dlsym(RTLD_NEXT, "read");
    sleep(5);
    printf("read sleep 5s\n");
    return origin_read(fd, buf, count);
}

usage:

1. gcc -shared -fPIC hook_read.c -o libhook_read.so -ldl;
2. before run apps export LD_PRELOAD=pwd/libhook_read.so;
3. run apps under this shell;
4. after running export LD_PRELOAD=""