NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/comp/lang/c/11485

Text File | 1992-07-22 | 2.7 KB | 78 lines

Newsgroups: comp.lang.c
Path: sparky!uunet!gatech!asuvax!ennews!envmsa.eas.asu.edu!ptran
From: [e-mail] (Phi-Long Tran)
Subject: Re: While problem
Message-ID: <[e-mail]>
News-Software: VAX/VMS VNEWS 1.4-b1
Sender: [e-mail] (USENET News System)
Organization: Arizona State University, Tempe, AZ
References: <[e-mail]>
Date: Wed, 22 Jul 1992 23:53:00 GMT
Lines: 65

In article <[e-mail]>, [e-mail] writes...

>   I'm having trouble with a whil loop in function I am writing to
>read a line from a fileby puttingeach character into an array, accesed by
>pionters, until the '\n' character is reached of EOF is reached.
>Trouble is, I keep getting an error message that the function needs an
>Lvalue (address) inside the while loop.  Any ideas as to the problem?
>The filename is a global variable, and that's why it isn't declared.

>char readline(char *string[])
>{
>  int i=0;
>
>  while(((*string+i++=(char)getc(fname))!=EOF)
>      &&((*string+i++=(char)getc(fname))!='\n'));
>  return (*string+(i-1));
>}

     I commend your courage for even attempting to write this kind of
gobbledegook -- I don't think even B. Kernighan or D. Ritchie would even
try this stuff, let alone P.J.  Plauger.

     Here are my observations:

1) Function getc accepts a file pointer ("FILE *"), *NOT* a file name.  You
can find this out in *ANY* book on C -- just look for a description of the
routine.

2) You are doing too many things at once to even possibly debug reliably.
Do you really understand all those operators, their precedence, their
side-effects, etc. ad inifitum. et. al.

3) To read in a line of text, you do not need an array of pointers (that's
what "char *string[]" is and means).  You just need an array of characters
into which a file I/O routine will fill with the characters.

4) Why are you performing arithmetic operations on the left side of an
assignment statement?  Look in a C book on making assignments.

     If all you want to do is read in a string, then there are many
standard library functions you can call:  fgets, gets, fscanf, scanf ...
They are declared in the header file "stdio.h" that you include in a module
when you use them.

     #define MAX_INPUT_CHARS 132 /* Or some relevant value. */

     ...

     char szData[MAX_INPUT_CHARS];
     FILE *pfileInput;           /* Pointer to a file for input. */

     ...

     if (fgets( szData, sizeof( szData ), pfileInput) == NULL)
     {
        /* An error occurred. */
     }

     Above all ... LOOK IT UP IN A C BOOK.  Only post when you have
EXHAUSTED your resources for information.  Have you looked this problem up?

---
Phi-Long Tran
[e-mail]
Arizona State University