Re: [Dev-C++] Reading file with getc(fp)

[Luigi S. <gi...@li...>]

At 18:47 09/04/02 -0700, rchavez wrote:
>Hi,
>
>I am trying to read a text file in a C program.  This code runs fine on the
>unix C environments I can access but gives a fatal error that removes the
>console window in Dev-C++ environment.

I have attempted to run you code and the same thing happened to me, I think 
the reason is: when the file named "word.h" does not exist, fp is assigned 
a NULL value, so your code attempts to read something using a NULL pointer, 
as a result, a run time error occurs.


>There are no warnings at compile time.

I shall not agree, in fact I tried to compile your code (using Dev-C++ 4.0 
with MinGW 2.95) after setting these additional options:
-Wall -Wnested-externs -Wredundant-decls

Here is what I get in the "Compiler" panel:

4 c:\mail\rob\orig.c warning: return-type defaults to `int'
7 c:\mail\rob\orig.c warning: nested extern declaration of `fopen'
7 c:\mail\rob\orig.c warning: redundant redeclaration of `fopen' in same scope
179 c:\progra~2\dev-c_~1\include\stdio.h warning: previous declaration of 
`fopen'
13 c:\mail\rob\orig.c warning: implicit declaration of function `system'
C:\mail\rob\orig.c compiled successfully

As you can see these are only warnings, so code is generated at your own 
risk! :)
Anyway, at compile time one can't catch run time errors.

>   It is definitely the getc() that causes the trouble because the program
>works in Dev-C++ when I use getch() and take input from standard input.

I do not know what the function "getch()" does, one thing I'm sure of, is 
that it is  not ANSI C 89.

>    Four questions:
>
>1. How do I make it work with Dev-C++ ?

Try the code I wrote below, it works on my machine (Win98SE, Dev-C++ 4.0, 
MinGW 2.95).

Note, if you are using my same version of Dev-C++, make sure that:
"Options"->"Compiler Options"->"Linker"->"compile for Win32 (no console)"
is unset, otherwise you will see nothing displayed on the screen.


>2. There was lots of talk on getch() and getchar() in the archives but
>nothing on getc().  Is getc() no longer ANSI C ?

Don't know what ANSI C99 says, however, since "getc" is in C89, I suppose 
it is still supported

>3. getch() swallows the cntrl-Z so I can't properly terminate using std
>input.  How do I overcome this when I want to use getch()?

As I said above, getch() is not a standard function.

>4.  Why is EOF cntrl-Z instead of cntrl-D in Dev-C?

This is not related to Dev, it has to do with the differences between Dos 
and Unix.
Since Dos came after Unix, I see no reason why to assume different 
conventions (another one I don't understand is the backslash and the slash 
issue).

>Your help will be greatly appreciated

hope it solves the problem

>and you people are wonderful to give so much help to the clueless like me 
>on this list!
>Rob.
>
>-----------------  my code --------------------------
>
>#include <stdio.h>
>
>main()
>{
>
>int c;
>FILE *fopen(), *fp;
>
>fp = fopen("words.h","r");
>while ( (c = getc(fp)) != EOF )
>   printf("\ngot a char %c",c);
>
>   system("PAUSE");                /** added this for Dev-C++ **/
>       return 0;
>}

You need to add no special line of code if you run console applications 
from the ... console! :)

Also remember that using function "PAUSE" makes program not portable to 
Unix (where there is no command named "PAUSE").

/* file test.c */
#include <stdio.h>
#include <errno.h>

#define FILENAME "words.h" /* name of file to be read */

int
main()
{

   FILE* fp = fopen(FILENAME,"r"); /* the file */

   if (fp == NULL)     /* unable to open file */
     perror(FILENAME); /* notify user */
   else /* ok, file is open */
     {
       int c; /* the character read from the file */

       while ((c = getc(fp)) != EOF)     /* found a character */
         printf("\ngot a char %c", c);   /* display the character */
     }

   return 0;
}

--

Luigi
gi...@li...