Text File Handling

nishkarsh · 08-24-2008, 10:04 AM

The code below to append a file is giving segmentation fault...
It takes the input but doesnt print DONE..
Plz help me out...

Code:

#include <stdio.h>

main() {
	char * ptr;	
	printf("\nName the file: ");	
	scanf("%s",ptr);
	FILE *f=fopen(ptr,"a");
	if(f) {
		fprintf(f,"The file is appended here\n");
		fclose(f);
	}
	printf("\nDONE!\n");
}

**Salem** · 08-24-2008, 10:14 AM

ptr isn't allocated any space, so when you read in your string it goes to a random place in memory.
In your case, in this instance, it blows up.

Allocate some space, or just use a char array.

> FILE *f=fopen(ptr,"a");
Mixing declarations and statements is not allowed in regular C

Also, be specific about main returning int, and actually return something.

nishkarsh · 08-24-2008, 10:31 AM

Thx for your reply...
I've made the changes u suggested... but the prob still persists...

the modified code is;

Code:

#include <stdio.h>

int main() {
	char name[20];
	printf("\nName the file: ");	
	scanf("%s",name);
	FILE *f;
	f=fopen(name,"a");
	if(f) {
		fprintf(f,"The file is appended here\n");
		fclose(f);
	}
	printf("\nDONE!\n");
	return 0;
}

arpsmack · 08-24-2008, 11:26 AM

Quote:

Originally Posted by Salem

> FILE *f=fopen(ptr,"a");
Mixing declarations and statements is not allowed in regular C

I guess that depends on what you mean by "regular C". C90 might not allow this, but I'm pretty sure C99 will.

Also, I don't have any problems compiling and running your code. Are you sure you aren't trying to enter a filename that's too large for the buffer?

nishkarsh · 08-24-2008, 11:48 AM

its working now
thanks ppl

08-24-2008, 10:04 AM	#1
nishkarsh Registered User Join Date: Aug 2008 Posts: 15	Text File Handling - seg fault The code below to append a file is giving segmentation fault... It takes the input but doesnt print DONE.. Plz help me out... Code: #include <stdio.h> main() { char * ptr; printf("\nName the file: "); scanf("%s",ptr); FILE f=fopen(ptr,"a"); if(f) { fprintf(f,"The file is appended here\n"); fclose(f); } printf("\nDONE!\n"); } Last edited by Salem; 08-24-2008 at 10:12 AM. Reason: Code is not written in italics*
nishkarsh is offline

08-24-2008, 10:14 AM	#2
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	ptr isn't allocated any space, so when you read in your string it goes to a random place in memory. In your case, in this instance, it blows up. Allocate some space, or just use a char array. > FILE *f=fopen(ptr,"a"); Mixing declarations and statements is not allowed in regular C Also, be specific about main returning int, and actually return something. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
Salem is offline

08-24-2008, 10:31 AM	#3
nishkarsh Registered User Join Date: Aug 2008 Posts: 15	Thx for your reply... I've made the changes u suggested... but the prob still persists... the modified code is; Code: #include <stdio.h> int main() { char name[20]; printf("\nName the file: "); scanf("%s",name); FILE *f; f=fopen(name,"a"); if(f) { fprintf(f,"The file is appended here\n"); fclose(f); } printf("\nDONE!\n"); return 0; }
nishkarsh is offline

08-24-2008, 11:48 AM	#5
nishkarsh Registered User Join Date: Aug 2008 Posts: 15	its working now thanks ppl
nishkarsh is offline

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