An example of Exception Handling source code

This snippet submitted by Ali Nawkhas Murad on 2012-01-25. It has been viewed 16545 times.
Rating of 5.3 with 139 votes

// 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<<"\n\t 1 file copied.\n";
		flag = 0;
	}
	if( flag != 0 )
	{
		cerr<<"\nWrong argument list!!!\n\n";
		return -1;
	}
	return 0;
}

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