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write the following in cpp
The task_3.cpp file holds the main() function which is responsible for the following functionality:
Extracts the input file name and output file name from the command line arguments.
Calls the appropriate openFile() function (see description below) to open the relevant files. If the file
name returned by openFile() is different from the one originally specified in the command line,
require the user to confirm to proceed with processing or to quit. Please use the prompts shown in
the sample runs provided below.
Each openFile() function should provide the following functionality:
attempts to open the passed in file name.
If there is an error when opening the provided file name the function should throw an exception,
passing whatever information is required to the exception handler. Please use the error messages
shown in the sample runs below.
The exception handler should display an appropriate error message and prompt the user to provide
a new file name, again please use the prompts shown in the sample runs below. The exception
handler should then recursively call openFile() passing the new file name. The openFile() function
will continue to be recursively called until a file is successfully opened. In practice you would put a
limit on the number of potential calls, in order to avoid infinite recursion. For this assignment please
disregard this problem.
The relevant exception class for the two openFile() functions are shown below.
o string openFile(ifstream& in, string str): Input file exception class is
class Readfile_error : public logic_error{
public:
Readfile_error (string reason);
}
o string openFile(ofstream& out, string str): Output file Exception class is
class Writefile_error : public logic_error{
public:
Writefile_error (string reason);
};
Return the name of the opened file.
sample run example
Cannot open input file, do not proceed with processing:
C:csc2402>a dat.txt out.txt
Cannot open data file dat.txt. Please input the correct data file name: daat.txt
Cannot open data file daat.txt. Please input the correct data file name: dtta.txt
Cannot open data file dtta.txt. Please input the correct data file name: data.txt
Cannot open dat.txt, data.txt opened instead.
Do you want to proceed? (‘y’ to proceed)n
Cannot proceed further. Program is closing down.
Expert Answer
#include <fstream>
#include <string.h>
#include <stdlib.h>
using namespace std;
int attempt=0;
char* openFile(ifstream& in,char* str) {
in.open(str);
if (!in) {
std::cerr << “File failed to open”;
cout << “Cannot open input file, do not proceed with processing!n”;
exit(0);
}
else{
return str;
}
}
char* openFile(ofstream& o, char* str) {
char * fileName;
o.open(str);
if(!o) {
std::cerr << “File failed to open”;
cout << “Cannot open data file “<<str<<“. Please input the correct data file name: “;
cin >> fileName;
attempt++;
openFile(o,fileName);
if(attempt==3) {
exit(0);
}
}else {
return str;
}
};
int main(int argc, char *argv[])
{
std::ifstream ifs;
ofstream ofs;
char flag;
string inputFileResult = openFile(ifs, argv[1]) ;
string outputFileResult = openFile(ofs, argv[2]) ;
if(attempt>0) {
cout<<“Cannot open”<<argv[2]<<“, “<<outputFileResult<<” opened insteadnDo you want to proceed? (‘y’ to proceed)”;
cin>>flag;
if(flag!=’y’) {
cout<<“Cannot proceed further. Program is closing down.”;
} else {
cout <<inputFileResult <<” “<<outputFileResult << endl;
}
}else{
cout <<inputFileResult <<” “<<outputFileResult << endl;
}
return 0;
}
