reading from end to beginnig of file

[liaa]

I know i am supposed to use fseek...what i don't understand is how does it work
I am trying to read character by character starting from last to first from a file and writing them in another one(reversing bytes)
I tried:

fseek(file1,0,SEEK_END);
ch=fgetc(file1)

but obviously there's something wrong with it...

[vart]

your fseek sets the file pointer at the end of file. It means - AFTER the last byte.

Do you really hope to read something there?

Step 1 byte to the beginning to read it...

[liaa]

then

        int i=1;
	char ch;
	do{

		fseek(file1,i,SEEK_END);
		ch=getc(file1);
		fputc(ch,file2);
		i+=1;

	}while(WHATs the CONDITION here)

thanks

[vart]

when i is > 0 - you are trying to go beyond the end-of-file, so you moving in the wrong direction

use ftell to determine how many bytes you need to read

[liaa]

thank you i got it working
only, it prints these characters in my output file before the actual text. :
ÿÿÿÿ
I'm thninking it has sth to do with unix EOF or CR :-??

[matsp]

thank you i got it working
only, it prints these characters in my output file before the actual text. :
ÿÿÿÿ
I'm thninking it has sth to do with unix EOF or CR :-??

Could you post the actual code?

--
Mats

[liaa]

#include<stdio.h>

int main( int argc, char* argv[])
{
	FILE* file1= fopen(argv[1],"r");
	FILE* file2= fopen("output","w");
	if((file1==NULL)||(file2==NULL))
		printf("open error!\n");
	else {
        int i=2,pos;
	char ch;
	fseek(file1,0,SEEK_END);
	pos=ftell(file1);
	
        while(pos>0)
	{		
		ch=getc(file1);
		fputc(ch,file2);
		pos--;
		fseek(file1,i,SEEK_END);
		i--;
	}
	fclose(file1);
	fclose(file2);
}
	return 0;

}

[liaa]

my mistake again should have initialized i= -2 ;
and first
fseek(file1,-1,SEEK_END);

[matsp]

Ok, a few corrections needed:
1. Start i with -1 (since "end-of-file-1" is one character from the end).
2. Move fseek() to BEFORE the fgetc(). Otherwise, you read the FIRST character first, then jump to the end.

--
Mats