Programming Forums > Application Development > C++

jademan · Dec 16th, 2005, 4:59 PM

So iv got a code like this...

ofstream file("C:/"+var+".txt);

I know this isnt right. I used PHP syntax just to deminstrate what I want to do.
Basically I want to insert a variable into the file string. Im sure its something simple but I just couldnt figure it out.

B3TA_SCR1PT3R · Dec 16th, 2005, 5:05 PM

firstly:

(Toggle Plain Text)

 ofstream file("C:\\"<<var<<".txt);

and if its not letting you put variables in(not sure havent worked with C++ in a while)
do:

(Toggle Plain Text)

string thefile = "C:\\";
string p = ".txt";
string s = thefile += var += p;
ofstream file(s);

(not sure if itll work)

jademan · Dec 16th, 2005, 5:14 PM

ofstream file("C://"<<var<<".txt");

That gave me this error -

error C2296: '<<' : illegal, left operand has type 'char [64]'

I tried this ...

char prepath[100] = "C:/Documents and Settings/All Users/Desktop/";
char extension[6] = ".html";
char path[150] = prepath + var + extension;
ofstream rep(path);

"var" is an integer btw

I got this error

error C2110: cannot add two pointers

B3TA_SCR1PT3R · Dec 16th, 2005, 5:16 PM

ok if your on Windows XP you use: C:\ not C:/

jademan · Dec 16th, 2005, 5:20 PM

yes i know that but that isnt the issue

DaWei · Dec 16th, 2005, 5:55 PM

Quote:

"C://"<<var<<".txt"

This does not concatenate strings in C++. Beta, please do not mislead new coders. Check your answers first. You may cause far more harm than good.

If you wish to concatenate C strings (character arrays terminated by nul characters), use the strcpy/strcat family of functions. If you wish to use C++ strings, you may use the '+' operator. Arguments requiring C strings will not accept C++ strings directly, however. You may specify the C string portion with myString.c_str (). That is not modifiable, only readable.

If you read the documentation for the things covered and still have questions, post back.

nnxion · Dec 16th, 2005, 6:35 PM

Why are you using C strings and not C++ strings?

This should work for you:

(Toggle Plain Text)

#include <iostream>
#include <string>

using namespace std;

int main()
{
	string prepath = "C:/Documents and Settings/All Users/Desktop/";
	string extension = ".html";

	string var = "bla";

	string path = prepath + var + extension;

	cout << path << endl;
	//ofstream rep(path);
	return 0;
}

DaWei · Dec 16th, 2005, 7:10 PM

He can't use the string directly in the open statement. He has to use a C string, if only by using filename.c_str ().

nnxion · Dec 16th, 2005, 7:53 PM

David as usual, you are correct. I'm not wanting to state the obvious

.

jademan · Dec 16th, 2005, 9:26 PM

yea im not using .net so I dont think "string" works ( visual C++ btw ) but i will research that other suggestion. Thank you

Dec 16th, 2005, 4:59 PM	#1
jademan Newbie Join Date: Dec 2005 Posts: 6 Rep Power: 0	ofstream insert variable So iv got a code like this... ofstream file("C:/"+var+".txt); I know this isnt right. I used PHP syntax just to deminstrate what I want to do. Basically I want to insert a variable into the file string. Im sure its something simple but I just couldnt figure it out.

Dec 16th, 2005, 5:05 PM	#2
B3TA_SCR1PT3R Hobbyist Programmer Join Date: Jul 2005 Location: Dallas, Texas Posts: 101 Rep Power: 0	firstly: (Toggle Plain Text) ofstream file("C:\\"<<var<<".txt); ofstream file("C:\\"<<var<<".txt); and if its not letting you put variables in(not sure havent worked with C++ in a while) do: (Toggle Plain Text) string thefile = "C:\\"; string p = ".txt"; string s = thefile += var += p; ofstream file(s); string thefile = "C:\\"; string p = ".txt"; string s = thefile += var += p; ofstream file(s); (not sure if itll work) __________________ Hoes telling me to calm down but I'm like fuck that shit!

Dec 16th, 2005, 5:14 PM	#3
jademan Newbie Join Date: Dec 2005 Posts: 6 Rep Power: 0	not working ofstream file("C://"<<var<<".txt"); That gave me this error - error C2296: '<<' : illegal, left operand has type 'char [64]' I tried this ... char prepath[100] = "C:/Documents and Settings/All Users/Desktop/"; char extension[6] = ".html"; char path[150] = prepath + var + extension; ofstream rep(path); "var" is an integer btw I got this error error C2110: cannot add two pointers

Dec 16th, 2005, 5:16 PM	#4
B3TA_SCR1PT3R Hobbyist Programmer Join Date: Jul 2005 Location: Dallas, Texas Posts: 101 Rep Power: 0	ok if your on Windows XP you use: C:\ not C:/ __________________ Hoes telling me to calm down but I'm like fuck that shit!

Dec 16th, 2005, 6:35 PM	#7
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	Why are you using C strings and not C++ strings? This should work for you: (Toggle Plain Text) #include <iostream> #include <string> using namespace std; int main() { string prepath = "C:/Documents and Settings/All Users/Desktop/"; string extension = ".html"; string var = "bla"; string path = prepath + var + extension; cout << path << endl; //ofstream rep(path); return 0; } #include <iostream> #include <string> using namespace std; int main() { string prepath = "C:/Documents and Settings/All Users/Desktop/"; string extension = ".html"; string var = "bla"; string path = prepath + var + extension; cout << path << endl; //ofstream rep(path); return 0; } __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

Dec 16th, 2005, 5:20 PM	#5
jademan Newbie Join Date: Dec 2005 Posts: 6 Rep Power: 0	yes i know that but that isnt the issue

Dec 16th, 2005, 7:10 PM	#8
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	He can't use the string directly in the open statement. He has to use a C string, if only by using filename.c_str (). __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Dec 16th, 2005, 7:53 PM	#9
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	David as usual, you are correct. I'm not wanting to state the obvious . __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

Dec 16th, 2005, 9:26 PM	#10
jademan Newbie Join Date: Dec 2005 Posts: 6 Rep Power: 0	yea im not using .net so I dont think "string" works ( visual C++ btw ) but i will research that other suggestion. Thank you

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Programming Forums > Application Development > C++

ofstream insert variable