Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!uokmax!servalan!epmooch!ben
From: ben@epmooch.UUCP (Rev. Ben A. Mesander)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: SAS C Bug??  Standard FILE command does not work!!
Message-ID: <ben.4666@epmooch.UUCP>
Date: 27 Jan 91 01:25:45 GMT
References: <1991Jan27.221835.1230@rodan.acs.syr.edu>
Lines: 63

>In article <1991Jan27.221835.1230@rodan.acs.syr.edu> goldberg@rodan.acs.syr.edu (Ross Goldberg) writes:
>I am trying to get a procedure working to read and write records to the
>disk.  This is accomplished in many books by using fwrite and fread.
>The sample below comes from one of the books...the problem is:
[...]
>#include <stdio.h>
>main ()
>{
> typedef struct {
>       char name[15];
>       int midterm;
>  } grades;
>int i,number;
>char name[50];
>grades student;
>FILE *fp;
>printf("class file  ");
>scanf("%s",name);
>if (NULL!=(fp=fopen(name,"w"))) {
>   printf("number of students");
>   scanf("%d",&number);
>   for (i=0;i<number;i=i+1) {
>     printf("student's name:  ");
>     scanf("%[^\n]",student.name);
>     printf("midterm score:  ");
>     scanf("%d",&(student.midterm));
>     fwrite (&student,sizeof(student),1,fp);
      ^^^^^^  ^^^^^^^^
>   }
[...]
>There is the book sample.
>As I said, where you see the fwrite (&student,sizeof(student),1,fp);
>it gives the warning for the &student    
>Ross Goldberg

From the Fine Manual for SAS/C:

SYNOPSIS

#include	<stdio.h>

a = fwrite(b,size,n,fp);

int	a;	actual number of blocks
char	*b;	pointer to first block
^^^^^^^^^^
int	bsize;	size of block in bytes
int	n;	maximum number of blocks
FILE	*fp;	file pointer

So, the first argument to fwrite needs to be a pointer to a character. 
You need to cast the pointer to your structure to a pointer to a character.
This is consistent with the definition of the C language, and is evidently
a bug in the program you typed in. Was the book pre-ANSI? I don't know,
my ancient UNIX reference manual lists the first argument to fwrite() as
a pointer to a character, so it's been that way for a very long time. 

Those books aren't perfect, you know!

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