Thread: Error in code - please help

ch should be an int (fgetc returns an int so that EOF can be distinguished from all possible char bit patterns).
You are using == (equality comparison) when you mean to use = (assignment).
You need to compare to EOF to test for the end of the file.

Code:

#include <stdio.h>
#include <stdlib.h>
 
int main()
{
    FILE *fin = fopen("test.txt","r");
 
    if (!fin)
    {
        puts("File not found.");
        exit(EXIT_FAILURE);
    }
 
    for (int ch; (ch = fgetc(fin)) != EOF; )
    {
        putchar(ch);
    }
 
    fclose(fin);
 
    return 0;
}

Originally Posted by Paderi

How do you get that code to output to the printer?

Assuming you're on Windows, I don't know exactly.
Either you can open up some special "file" as the printer and output to that.
Or you can redirect the output to the printer on the command line.
Or you can output to a file and use system() to run a program to print the file.
Hopefully someone else can fill you in on the details.

Originally Posted by john.c

Assuming you're on Windows, I don't know exactly.
Either you can open up some special "file" as the printer and output to that.
Or you can redirect the output to the printer on the command line.
Or you can output to a file and use system() to run a program to print the file.
Hopefully someone else can fill you in on the details.

This is very useful, thank you.

Given: in fputc(ch,stdout);

I am wanting to use the code on a W10 box. I was hoping that it would be possible to redefine "stdout" as the default printer. Else stdout leads to the display.

I found the code below upon further searching for information, however, the code does not work: "error opening printer". Please help.

Code:

int main(void) 
{ 
  FILE *prnt;
  
  prnt = fopen("/dev/lpt1", "w"); 
  if (prnt)
    fprintf(prnt, "This is a test.\n"); 
  else
    printf ("error opening printer\n");
  fclose(prnt); 
  return 0;
}

Well in DOS/Windows there is no /dev, that comes from Unix/Linux land.

Which compiler are you using?

Also, where is your printer plugged into your PC?
- a real printer port (like your machine is 20 years old, and so is your printer)
- a USB port
- some other machine on the local network, or is a network attached printer.

If it's a network/USB printer, then you may need to use the 'net use' command to associate the new device with the old DOS-style device name.
Net use | Microsoft Docs

You could try one of these to begin with.

Code:

prnt = fopen("PRN", "w"); 
prnt = fopen("PRN:", "w"); 
prnt = fopen("LPT", "w"); // and the appended : variant
prnt = fopen("LPT1", "w"); // and the appended : variant

In each case, see if you end up with a text file if you don't see printer output, and you don't see "error opening printer".

> fprintf(prnt, "This is a test.\n");
You should also finish by sending a \f (form-feed) to cause the printer to complete the page.
Eg.
fprintf(prnt, "This is a test.\n\f");

Originally Posted by Salem

Well in DOS/Windows there is no /dev, that comes from Unix/Linux land.

<snipped>;

Thank you, Salem. for responding.

I tried via network printing, and by connecting the printer to the PC. It looks like LPT is being accepted, nevertheless the printer isn't responding. I am no longer expecting to get to the bottom of this. (As to my PC and printer. they are both recent enough. (An I7 processor.)

What is the output of the command: net use
How about: wmic printer list brief

It's a matter of how to refer to the printer in C code. In the past you could say stdprn or "LPT1". If you answer my questions (by typing the commands into a console and posting the output) we might be able to do something similar.

Forget it.