fopen, include string in filename.

lenxe · 03-09-2009, 08:13 AM

Hi
i'm trying to get the user to enter a string as the save name then to save it as a text file under that string. I'm a beginer to c but have used other languages if that helps. (this needs to be done in c as it is part of a project) heres what i've guessed at

Code:

char teststring[51];
FILE * testFILE;

/* program code here*/

printf("please enter the save name?");
		scanf("%s",&teststring);

		testFILE = fopen ("F:\\Programming_output\\"+teststring+".txt","w");
		fprintf(testFILE, "saved data here");
		fclose (testFILE);

i've had a look around and fstream has been mentioned but after trying this i get more errors.

MK27 · 03-09-2009, 08:41 AM

Quote:

Originally Posted by lenxe

I'm a beginer to c but have used other languages if that helps.

So you just expect it to be that easy then, eh?

You can't use variables in C "string literals", unfortunately.

Code:

		testFILE = fopen ("F:\\Programming_output\\"+teststring+".txt","w");

Having come from "other languages" myself I thot this a bit ridiculous at first, but you will have to construct a string if you want to do anything beyond the literal, eg. "F:\\Programming_output\\myfile.txt" is fine. You have at least two choices on how to do this:

Code:

OPTION #1
        char fullname[256]="F:\\Programming_output\\";
        strcat(fullname,teststring);
        strcat(fullname,".txt"); 
OPTION #2
        char fullname[256];
        sprintf(fullname, "F:\\Programming_output\\%s.txt",teststring);

Then you can use testFILE = fopen (fullname,"w");

Meldreth · 03-09-2009, 08:46 AM

c doesn't let you concatenate strings with +, you need to format the strings together with sprintf or use something like strcat to do the job. i think sprintf is better for this, so here's an example.

Code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    char fileName[51];
    char fullPath[80];
    printf("Save As: ");
    fflush(stdout);
    if (gets(fileName))
    {
        sprintf(fullPath, "F:\\Programming_output\\%s.txt", fileName);
        puts(fullPath);
    }
    return EXIT_SUCCESS;
}

lenxe · 03-09-2009, 08:59 AM

thanks for the quick replies. i've got a working method i used the strcat methoad as i know how this is working. (i've not come across sprintf before.) after seeing this it does make logical sence. thanks again.lewis

03-09-2009, 08:13 AM	#1
lenxe Registered User Join Date: Mar 2009 Posts: 2	fopen, include string in filename.(SOLVED) Hi i'm trying to get the user to enter a string as the save name then to save it as a text file under that string. I'm a beginer to c but have used other languages if that helps. (this needs to be done in c as it is part of a project) heres what i've guessed at Code: char teststring[51]; FILE * testFILE; /* program code here/ printf("please enter the save name?"); scanf("%s",&teststring); testFILE = fopen ("F:\\Programming_output\\"+teststring+".txt","w"); fprintf(testFILE, "saved data here"); fclose (testFILE); i've had a look around and fstream has been mentioned but after trying this i get more errors. Last edited by lenxe; 03-09-2009 at 09:00 AM. Reason: correction*
lenxe is offline

03-09-2009, 08:46 AM	#3
Meldreth Registered User Join Date: Feb 2009 Posts: 138	c doesn't let you concatenate strings with +, you need to format the strings together with sprintf or use something like strcat to do the job. i think sprintf is better for this, so here's an example. Code: #include <stdio.h> #include <stdlib.h> int main() { char fileName[51]; char fullPath[80]; printf("Save As: "); fflush(stdout); if (gets(fileName)) { sprintf(fullPath, "F:\\Programming_output\\%s.txt", fileName); puts(fullPath); } return EXIT_SUCCESS; }
Meldreth is offline

03-09-2009, 08:59 AM	#4
lenxe Registered User Join Date: Mar 2009 Posts: 2	thanks for the quick replies. i've got a working method i used the strcat methoad as i know how this is working. (i've not come across sprintf before.) after seeing this it does make logical sence. thanks again.lewis
lenxe is offline

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