simple example of dlsym()

test-dlsym.c

/*
 * Quick example to test dlsym()
 * build: gcc -W -Wall -Werror -o test-dlsym test-dlsym.c
 * Usage: ./test-dlsym openldap
 */

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

typedef struct package_data PackageData;
struct package_data
{
   const char * identifier;
   const char * name;
   const char * website;
   const char * version;
   const char * license;
};

const PackageData pkgdata_cyrus_sasl =
{
   "cyrus_sasl", "Cyrus SASL", "http://asg.web.cmu.edu/sasl/", "2.1.23", NULL
};

const PackageData pkgdata_openldap =
{
   "openldap", "OpenLDAP", "http://www.openldap.org/", "2.4.22", NULL
};

const PackageData pkgdata_openssl =
{
   "openssl", "OpenSSL SSL/TLS Toolkit", "http://www.openssl.org/", "1.0.0a", NULL
};

const PackageData pkgdata_pcre =
{
   "pcre", "Perl Compatible Regular Expressions", "http://www.pcre.org/", "8.10", NULL
};

int main(int argc, char * argv[])
{
   char                symbol_name[512];
   unsigned            u;
   const PackageData * datap;

   if (argc != 2)
   {
      fprintf(stderr, "Usage: %s <identifier>\n", argv[0]);
      return(1);
   };

   snprintf(symbol_name, 512, "pkgdata_%s", argv[1]);
   for(u = 0; u < strlen(symbol_name); u++)
   {
      if ((symbol_name[u] >= 'A') && (symbol_name[u] <= 'Z'))
         symbol_name[u] = symbol_name[u] - 'A' +'a';
      else if ( ((symbol_name[u] < 'a') || (symbol_name[u] > 'z')) &&
                ((symbol_name[u] < '0') || (symbol_name[u] > '9')) )
         symbol_name[u] = '_';
   };

   if (!(datap = (const struct package_data *) dlsym(RTLD_SELF, symbol_name)))
   {
      fprintf(stderr, "%s: unknown package -- %s\n", argv[0], argv[1]);
      return(1);
   };

   printf("Identifier: %s\n", datap->identifier ? datap->identifier : "unknown");
   printf("Name:       %s\n", datap->name       ? datap->name       : "unknown");
   printf("Version:    %s\n", datap->version    ? datap->version    : "unknown");
   printf("Website:    %s\n", datap->website    ? datap->website    : "unknown");
   printf("License:    %s\n", datap->license    ? datap->license    : "unknown");

   return(0);
}