Passing a value while writing inside a file:C++ - c++

Question

I need to pass the value of one of the variables(containing the value of a path) to the contents of the file I am writing. The file outfile is of type ".ctl"
Lets say the file "outfile.ctl" gets created at location /abc/xyz
so I will be having /abc/xyz/outfile.ctl at this location. Now inside outfile.ctl file I have written some context. If you see the contents carefully I have included the line: file <<"file='filepath/Trial.data'\n"; which creates another file with the name Trial.data in the location filepath.Lets says filepath = /pqr/stu. So Ideally after the outfile.ctl file compiles I should have trial.data created at /pqr/stu llocation. I want to achieve this by the system command. But not getting the desired result created.Elaborated code is below
Snippet of the code.
void somefunc()
{
fstream file_1;
char outfile1[120],
filename[50] = "/abc/xyz/outfile.ctl";
char filepath[50] = "/pqr/stu/;
strcpy(outfile1, filename);
cout << outfile1;
cout << "\n";
file_1.open(outfile1, ios::out);
if (file_1) {
file_1 << "export\n";
file_1 << "client=000\n";
file_1 << "file='" << filepath << "/Trial.data'\n";
file_1 << "delete from BDRGIN\n";
file_1 << "select * from BDRGIN\n";
file_1.close();
system("R3trans outfile1");
}
Ideally the last line should create the trial data file in /pqr/stu/ folder but it doesnt. In my case it doesnot happen so , and a file outfile_1(without file extension) gets created in the folder where I am running the .cpp script. Can someone help?

Answer 1

It's not hard
file << "file='" << filepath << "/Trial.data'\n";
In C++ variables don't get substituted inside strings (unlike some scripting languages).
EDIT
You have basically made the same mistake again with your system command, variables don't get substituted inside strings. If you need a string variable which is made from other string variables you have to build up the string using strcpy and strcat. Try it like this
char cmd[250];
strcpy(cmd, "R3trans ");
strcat(cmd, outfile1);
cout << cmd << "\n"; // for testing
system(cmd);

Answer 2

You are missing a couple of things which I added:
You didn't include the output filename and filepath variables into your code, you didn't post all of your code to make in compilable.
Below is the code with "current path" (which we obtain with cwd in Linux) and your filename, included into your file "Trial.data" and written to the "current path/Trial.data" in you compile directory.
#include <iostream>
#include <fstream>
#include <string.h> //for strcat to concatinate the two (filepath+filename)
#include <unistd.h> //for getcwd to obtain your 'current path'
using namespace std;
int main(){
fstream file;
char cwd[256];
char *filepath= {getcwd(cwd, sizeof(cwd))}; // or write your path here instead
char filename[15] = "/Trial.data";
strcat(filepath, filename);
file.open(filepath,ios::out);
if(!file){
cout<<"File creation failed";
} else {
cout<<"New file created";
file <<"export\n";
file <<"client=000\n";
file <<"file='" << filepath << "'\n";
file <<"select * from HTTPURLLOC\n";
file.close(); // Step 5: Closing file
}
return 0;
}