dltest.c

Linux下的动态库生成方法及实例。很完整的。

/*************************************************************/
/*     Test Linux Dynamic Function Loading              */
/*                                      */
/*     void       *dlopen(const char *filename, int flag)           */
/*          Opens dynamic library and return handle     */
/*                                      */
/*     const char *dlerror(void)                    */
/*          Returns string describing the last error.           */
/*                                      */
/*     void       *dlsym(void *handle, char *symbol)            */
/*          Return pointer to symbol's load point.          */
/*          If symbol is undefined, NULL is returned.           */
/*                                      */
/*     int        dlclose (void *handle)                    */
/*          Close the dynamic library handle.               */
/*                                      */
/*                                      */
/*                                      */
/*************************************************************/
#include<stdio.h>
#include    <stdlib.h>
 
/*                              */
/* 1-dll include file and variables */
/*                              */
#include    <dlfcn.h>
void  *FunctionLib;     /*  Handle to shared lib file   */
int   (*Function)();        /*  Pointer to loaded routine   */
const char *dlError;        /*  Pointer to error string     */

char	dllName[10][128];
char	dllNameSo[128];
main( argc, argv )
{
  int   rc;             /*  return codes            */
  char HelloMessage[] = "HeLlO WoRlD\n";
  FILE	*fp;
  int 	i = 0, j;

  if((fp = fopen("dll.txt", "r")) == NULL){
  	printf("\nopen dll.txt fail");
	exit(0);
  }
  while(!feof(fp) && i < 10){
	fscanf(fp, "%s\n", dllName[i]);
	printf("\nread file \"%s\"", dllName[i]);
	i++;
  }
  printf("\nread %d dll file", i);
/*                              */
/* 2-print the original message                 */
/*                              */
  printf("\n  dlTest  2-Original message \n");
  printf("%s", HelloMessage);

/*                                               */
/*  3-Open Dynamic Loadable Libary with absolute path      */
/*                                              */
  for(j = 0; j < i; j++){
	sprintf(dllNameSo, "%s.so", dllName[j]);
	printf("\n Now use dll %s", dllNameSo);
	FunctionLib = dlopen(dllNameSo, RTLD_LAZY);
  	dlError = dlerror();
  	printf("  dlTest  3-Open Library %s return-%s- \n", dllNameSo, dlError);
  	if( dlError ) 
		exit(1);

  	Function = dlsym(FunctionLib, dllName[j]);
  	dlError = dlerror();
  	printf("  dlTest  4-Find symbol print %s return-%s- \n", dllNameSo, dlError);
  	if( dlError ) 
		exit(1);
  	rc = (*Function)( HelloMessage );
  	printf("  dlTest  5-print %s return-%s- \n", dllNameSo, dlError);

  	rc = dlclose(FunctionLib);
  	dlError = dlerror();
  	printf("  dlTest  6-Close handle return-%s-\n",dlError); 
  	if( rc ) 
		exit(1);
  }

  return(0);

}