程式碼：

//file：addVec.c

#include "vector.h"                                                                       

int gVal = 200;
int gVal2 = 1;

int addVec(int *xP, int *yP, int *zP, int Num){
    for(int i = 0; i < Num; i++){
        zP[i] = xP[i] + yP[i];
    }
    gVal += Num;

    return gVal + gVal2;
}

 
//vector.h
#ifndef vector_h
#define vector_h

int addVec(int *xP, int *yP, int *zP, int Num);                                           
void mulVec(int *xP, int *yP, int *zP, int Num);

#endif

//mulVector.c
#include "vector.h"                                                                       

void
 
 mulVec(int *xP, int *yP, int *zP, int Num){
    for(int i = 0; i < Num; i++){
        zP[i] = xP[i] * yP[i];
    }

    return;
}

//testVec.c
#include <stdio.h>
#include "vector.h"

int x[2] = {1, 2};
int y[2] = {3, 4};
int z[2];
    
extern int gVal;
extern int gVal2;                                                                         
    
 
int main(int argc, char **argv)
{   
    addVec(x, y, z, 2);
    printf("z = [%d %d]\n", z[0],  z[1]);

    return gVal + gVal2;
}

編譯動態庫：gcc -shared -fPIC -o libVector.so addVec.c mulVec.c

用動態庫編譯：gcc -g -I. -L. -lVector testVec.o -o testVec

修改變數：LD_LIBRARY_PATH

　　LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$PWD/.

　　echo $LD_LIBRARY_PATH 結果：:/home/nication/WORKM/studyCode/gnuC/chapter04/lib/shared2/. 沒有問題

　　export LD_LIBRARY_PATH

執行：./testVec

結果：z = [4 6]

檢視返回變數：echo $? 值為203 正常OK