reading from end to beginnig of file

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:

Code:

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

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

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...

then

Code:

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        int i=1;
        char ch;
        do{

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

        }while(WHATs the CONDITION here)

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thanks

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

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 :-?? :D

Quote:

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Originally Posted by 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 :-?? :D

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Could you post the actual code?

--
Mats

Code:

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#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;

}

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

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