Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!ames!apple!motcsd!hpda!hpcuhb!hp-ses!hpdml93!stephen
From: stephen@hpdml93.HP.COM (Stephen Holmstead)
Newsgroups: comp.sys.amiga
Subject: Re: C problems
Message-ID: <380023@hpdml93.HP.COM>
Date: 30 May 89 15:11:56 GMT
References: <May.29.21.40.18.1989.8866@topaz.rutgers.edu>
Organization: HP Disk Memory Division - Boise, ID
Lines: 78

>There's open, fopen, creat, etc... Which do I use when? What about writing to
>the console? Can anyone recommend a GOOD book that explains the
>various methods of I/O and also points out differences between
>"standard" and "machine specific"? 

Briefly, open, creat, write, etc. are lower-level I/O routines.  Each
process 'n' bytes of raw data.  fopen, fprintf, fclose, etc. are higher
level routines.  They will process "formatted" data.  For someone new to
'C', I recommend that you use the 'f..' commands (they are easier to
produce the desired result but are slower).  I assume that you have the
complete documentation on these, so I will only mention a few of the
command names...

fopen() -- opens a file and returns a file handle.
fclose() -- closes a file.
fprintf() -- just like 'printf' except to a file (formatted print).
fputs() -- put a string to a file.
fputc() -- put a character to a file.
fgets() -- get a string from a file.
fgetc() -- get a character from a file.
fscanf() -- formatted read (just like 'scanf').

>Also, here's some source I tried today. What I'm trying to do is
>simply copy one file to another. When I compile it, I get error 125
>which means "too many subscripts or indirection on integer". It occurs
>wherever I mention argv[x].
>
>#include <stdio.h>
>main(argc, argv)
*************
PROBLEM:  You forgot to tell the compiler the type of the input paramters.
          The compiler assumed that both were 'int' because you didn't
	  specify otherwise.
int argc;
char *argv[];
*************
>{
>	int c;
>	FILE *fp1, *fp2;
>		       	
>	if ((fp1=fopen(argv[1], "r"))==NULL) {
>		printf("Can't open %s", argv[1]);
>		exit();
>		}
>
>	if ((fp2=fopen(argv[2], "w"))==NULL) {
>		printf("Can't open %s", argv[2]);
>		exit();
>		}
>	
>	while ((c=getc(fp1)!=EOF)) 
>		putc(fp2);
>
>}

Just a couple of notes:
1. 'exit' requires a parameter which it returns to the operating system.
   Most people will return a negative number to indicate an error has
   occurred.  (format:  exit(-1);)
2. It is also common practice to make sure that there are at least
   enough arguments given before you assume they exist:
   if (argc<3)
   {
      printf ("Not enough arguments; format: %s <input_file> <output_file>\n",
              argv[0]);
      exit(-1);
   }

Otherwise, the code looks good.  Have fun with 'C'.

name:    Stephen Holmstead
phone:   (208) 323-2840
uucp:    hplabs!hpdmlge!stephen
uxmail:  stephen@hpdmlge
usmail:  Hewlett-Packard
         Disk Memory Division
         11413 Chinden Blvd
         Boise, ID 83714