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From: edw@IUS1.CS.CMU.EDU (Eddie Wyatt)
Newsgroups: comp.lang.c
Subject: Re: how to write a function that returns a string of N nulls
Message-ID: <206@PT.CS.CMU.EDU>
Date: Mon, 19-Oct-87 21:08:25 EDT
Article-I.D.: PT.206
Posted: Mon Oct 19 21:08:25 1987
Date-Received: Wed, 21-Oct-87 00:18:36 EDT
References: <507@umbc3.UMD.EDU>
Sender: netnews@PT.CS.CMU.EDU
Organization: Carnegie-Mellon University, CS/RI
Lines: 53

In article <507@umbc3.UMD.EDU>, dipto@umbc3.UMD.EDU (Dipto Chakravarty ) writes:
> 
> I have a prog that takes two parameters. The first one is a port and
> the second is an integer that specifies the length of the string to 
> be sent to this port.
> 
> If N=4 then I have to send a "\0\0\0\0" to the port. How can I write
> a function that will take N as a parameter and return a string _out
> (which consists of N "\0"s to my main(). 


char *build_null_string(N)
    int N;
    {
    char *temp;
    extern char *malloc();

    temp = malloc(sizeof(char)*N);  /*  I actually never include
					the sizeof(char) */
    bzero(temp,sizeof(char)*N);
    return(temp);
    }

> 
> And secondly what form of fprintf or fwrite do I use to print out the
> string from the main. The function itself can handle the output of the
> string if passing it as parameter is messsy. 
> 


   What you probably want something like this :

	#define 	WRITEBLOCK	4

	write_null_chars(N,port)
 	    register int N;
	    FILE *port;
	    {
	    register int i, j;
	    static char a[WRITEBLOCK];
  			/* The static array should contain only zeros */

	    for (i = N; i >= WRITEBLOCK; i -= WRITEBLOCK)
		fwrite(a,sizeof(char),WRITEBLOCK,port);

	    for (j = i; j > 0; j--)
		fwrite(a,sizeof(char),1,port);
	    }
-- 

					Eddie Wyatt

e-mail: edw@ius1.cs.cmu.edu