Thread: File problem

1)Many thanks, i just forgot to change the name of the file.. It works fine only if in the file there is just the number. When i wrote the file, i wrote the number and i wrote and an ENTER. When the programm works, it prints the right number and a box in black at the position of the enter. Why that ( if there isn't enter it doesn't print that box ) ?

2) I tried to make it in a more general form. This code should print all the characters uppercase:

Code:

#include <stdio.h>
#include <ctype.h>

int main()
{
	int a;
	long readpos, writepos;
	FILE *in;

	in=fopen("test.txt","r+");
	writepos = ftell(in);
	while( ( a = getc( in ) ) != feof( in )){
		readpos = ftell(in);    // where we need to get back to for reading
		fseek(in,writepos,SEEK_SET);   // go back to the writepos
		putc( toupper( a ), in );
		fflush(in);  
		fseek(in,readpos,SEEK_SET);     // go back to the readpos
	}
	fclose( in );

	return 0;
}

But it doesn't work. Why?

Also, can you explain me why we need the fflush ( in ) please?
Thanks

1)Thanks for your comments

2) Does this code ( the one about characters ) with these changes run fine in your computer?
Not in mine.

3) When should i use EOF and when feof( stream ) ?

4) I don't know if i have i hex editor, but, can you run that program and put an Enter after the number in the file and see the results and tell me what you think please?

5) About the fflush you said "make sure it happens before another file reading function". Can you explain that a little bit more please?

6) Sorry if i am getting tiring

&)Thanks in advance.

A last the code works!!
Many thanks.

But please, would you mind answering my question 3 ?

Thanks again.

Ok, thanks, i got it.

However, i just thought that we don't need the fflush(in) because the bufeer will be always empty since we get one-by one the characters and we don't use scanf(). But even if we used scanf we would use the %c so it would return fine without the need to read the next characcter.
Am i right?

Try this, Notice the do while statement while scaning and printing into the file~


#Include <stdio.h>



int main()
{
int num;
FILE *in;

in=fopen("test.txt","r+");
do
{
fscanf( in, "%d", &num );
fprintf( in, "%d", num * 10 );
}while (getchar(in))!=EOF);
fclose( in );

return 0;
}

try this,,notice that I have included the do ...while function, while reading and printing your file!

#include <stdio.h>

int main()
{
int num;
FILE *in;

in=fopen("test.txt","r+");
do
{
fscanf( in, "%d", &num );
fprintf( in, "%d", num * 10 );
}while (getchar(in))!=EOF);
fclose( in );

return 0;
}