#include <stdio.h>
    #include <setjmp.h>

    enum Error { NoError=0, DivByZero=1, FileError=2 };

    jmp_buf jumper;

    void run(char *astr, char *bstr, char *fileName) {  // try 的主程式
      int a = atoi(astr);
      int b = atoi(bstr);
      if (b == 0) // can't divide by 0
        longjmp(jumper, DivByZero);
      int result = a/b;
      FILE *file;
      if ((file=fopen(fileName, "w")) == NULL)
        longjmp(jumper, FileError);
      else {
        fprintf(file, "%d/%d=%d\n", a, b, result);
        printf("save to file %s : %d/%d=%d\n", fileName, a, b, result);
      }
      fclose(file);
    }

    int main(int argc, char *argv[]) {
      int error = setjmp(jumper); // try
      switch (error) {    //
        case NoError:    //
          run(argv[1], argv[2], argv[3]);    //     run();
          break;    //
        case DivByZero:    // catch DivByZero:
          printf("Error %d : Divide by zero\n", error);//    ...
          break;    //
        case FileError:    // catch FileError:
          printf("Error %d : File error\n", error);    //    ...
          break;    //
        default:    // default:
          printf("Error %d:Unhandled error\n", error);//    ...
      } 
    }