C++异常处理范例代码

// Program shows copying one text file from source location
// to any other location (destination),plus possibility of changing its name,// and also shows many language features in exception handling.
// This program should be run from the command prompt
  
#include<iostream>
#include<stdio.h>
#include<stdexcept>
  
using namespace std;
  
class PathError : public runtime_error
{
    public:
        PathError(const char *x) : runtime_error(x)
    {}
};
  
// function to open source file for read
  
FILE* source (char* argvs[])
{
    FILE *in;
    //open source file for read
    if((in = fopen(argvs[1],"r"))==NULL)
    {
        throw PathError("attempted to open wrong input file path");//terminate function
    }
    return in;
}
  
//function to create destination file for writting
FILE* destination (char* argvs[])
{
    FILE *out;
    //open destination file for write
    if((out = fopen(argvs[2],"w")) == NULL)
    {
        throw PathError("attempted to open wrong output file path");//terminate function
    }
    return out;
}
  
int main(int argc,char *argv[])
{
    FILE *in,*out;
    bool flag = 1;
    int temp;
    while(argc == 3)
    {
        try
        {
            in = source( argv );
            out = destination( argv );
            argc = 0;
        }
        catch(PathError& PathError)
        {
            cerr <<"nException occured: " << PathError.what() << endl;
            return -1;
        }
  
        while(!feof(in))//test for it is not end of input file
        {
            temp = fgetc(in);//get char from (in)file
            if( temp != EOF)
            {
                fputc(temp,out);//put char to (out) file
            }
        }
        fclose(in);
        fclose(out);
        cout<<"nt 1 file copied.n";
        flag = 0;
    }
    if( flag != 0 )
    {
        cerr<<"nWrong argument list!!!nn";
        return -1;
    }
    return 0;
}