/* fakesys.c */
#include <unistd.h>   /* for execvp */
#include <dlfcn.h>    /* for dlsym */
#include <stdio.h>

static int (*real_execvp)(const char *file, char *const argv[]);

int execvp(const char *file, char *const argv[]) {
    char *msg;
    
    /* lookup original shared lib function */
    real_execvp = dlsym(RTLD_NEXT, "execvp");   /* see dlsym(3) */
    if ( (msg = dlerror() ) != NULL ) {
        fprintf(stderr, "dlopen of execvp() failed : %s\n", msg);
    }
    
    fprintf(stderr, "calling execvp(\"%s\", ...)\n", file);
    
    /* execute original lib function */
    return real_execvp(file, argv);
}