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#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <getopt.h>
#include <string.h>
#include <dlfcn.h>
extern char *optarg;
extern int optind, opterr, optopt;
static struct option long_options[] = {
{"library", required_argument, 0, 'l'},
{"symbol", required_argument, 0, 's'},
{"help", no_argument, 0, 'h'},
{0, 0, 0, 0},
};
/* This array must parallel long_options[] */
static const char *descriptions[] = {
"specify a library path to look up symbol",
"specify symbol to look up",
"print this help screen",
};
void print_help(const char *name) {
fprintf(stdout,
"invokation:\n"
"\t%s [-l <libname>] -s <symbol name>\n"
"\t%s -h\n\n", name, name);
fprintf(stdout, "options:\n");
struct option *opt = long_options;
const char **desc = descriptions;
while (opt->name) {
fprintf(stdout, "\t-%c/--%s%s: %s\n",
opt->val,
opt->name,
(opt->has_arg ? " (argument)" : ""),
*desc);
opt++;
desc++;
}
}
int get_options(int argc, char **argv, char **lib, char **sym)
{
int c;
*lib = 0;
*sym = 0;
while (1) {
/* getopt_long stores the option index here. */
int option_index = 0;
c = getopt_long (argc, argv,
"l:s:h",
long_options,
&option_index);
/* Detect the end of the options. */
if (c == -1) break;
switch (c) {
case 'l':
*lib = strdup(optarg);
break;
case 's':
*sym = strdup(optarg);
break;
case 'h': print_help(argv[0]); exit(EXIT_FAILURE); break;
case '?':
/* getopt_long already printed an error message. */
break;
default:
fprintf(stderr, "Unknown option");
exit(EXIT_FAILURE);
}
}
return optind;
}
int main(int argc, char **argv)
{
char *libname, *symname, *prog = *argv;
get_options(argc, argv, &libname, &symname);
if (symname == NULL) {
fprintf(stderr, "You must specify a symbol!\n");
print_help(prog);
exit(EXIT_FAILURE);
}
{
const char *dlerr;
void *handle, *symbol;
printf("opening library [%s]\n", libname);
dlerr = dlerror();
handle = libname ? dlopen(libname, RTLD_NOW) : RTLD_DEFAULT;
dlerr = dlerror();
if (dlerr != NULL) fprintf(stderr, "dlopen() error: %s\n", dlerr);
printf("opening symbol [%s]\n", symname);
symbol = dlsym(handle, symname);
dlerr = dlerror();
if (dlerr != NULL) fprintf(stderr, "dlsym() error: %s\n", dlerr);
printf("closing library [%s]\n", libname);
dlclose(handle);
dlerr = dlerror();
if (dlerr != NULL) fprintf(stderr, "dlclose() error: %s\n", dlerr);
else printf("successfully opened symbol\n");
}
if (libname != NULL) free(libname);
if (symname != NULL) free(symname);
return 0;
}
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