• C

How do you go back a space when writing to a file?

Here's the question.......how do you go back a space in the file you are writing to?  When i do

fputc("\b", fpTextOut);  

all that happens is a box gets outputted in the file, but what i want to do is go back a space and write over the previously written text in the file being written to.....

It's not a hard question....please give syntax in the answer. Thanks!
itssookAsked:
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niemeyerCommented:

That's occurring because your command really insert the char '\b' into the file. You have to move the file pointer back...

fseek(fpTextOut,-1,SEEK_CUR);
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itssookAuthor Commented:
hey neimeyer,

that's right, it worked! Answer the question to get your points!
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zultiCommented:
you can give him points even if he didn't answer.
just click beside his comment
it say "accept comment as answer" or something like this.
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scrapdogCommented:
>fputc("\b", fpTextOut);  

This will insert the \b character in your file, as niemeyer said.  However, when your file is interpreted (i.e. dumped to the screen), the \b character may actually incite a backspace and the output would reflect this.

However, if you want to remove the char from the actual file, niemeyer's solution is what you want.
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hongjunCommented:
/* Assume file name to be read is "file.dat"
 * Assume contents of "file.dat" is (below)
 * 12345
 * Output of program execution is shown below
 * 12
 * File contents now would be
 * 1n345
 * Written to solve your problem
 * Hope it will helps
 */

#include <stdio.h>

void main()
{
    FILE *fp;
    char input;
    char replace='n';

    if ( (fp = fopen("file.dat","r+b")) == NULL )  /* open file as binary file */
        printf("Error in opening file.\n");
    else { /* file position now at 1st position */
        input = getc(fp); /* file position now at 2nd position after reading */
        printf("%c",input);
        input = getc(fp); /* file position now at 3rd position after reading */
        printf("%c\n",input);
        fseek(fp,-1,SEEK_CUR);   /* move file position back to 2nd position */
        fputc(replace,fp);   /* write the replace char to current position */
        fclose(fp);
    }
}
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niemeyerCommented:
Hi hongjun!!

I'm missing something or I've already answered this question 7 hours before you?

People here is very smart...  :-)
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itssookAuthor Commented:
neimeyer answered first if hee propesed an answer i'd give him the points
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niemeyerCommented:
You could consider my comment as an answer. But no problems... if it's better for you if I submit an answer... here it is! :-)

Thank you!
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hongjunCommented:
No offence neimeyer. I only trying to help.
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