NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/2074

Internet Message Format | 1996-08-05 | 1.7 KB

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: Question about system call
Date: Thu, 18 Jan 96 22:04:48 GMT
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Message-ID: <[e-mail]>
References: <4dekv8$[e-mail]> <[e-mail]>
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In article <[e-mail]>
           [e-mail] "Alun Champion" writes:

>: An example:
>
>:   write(0, (the integer value), sizeof(int));

>1) Try:
>
>  write(0, &int_value, sizeof(int));

That assumes (the integer value) is an lvalue, not a general expression (or
even a constant).

>2) Try:
>
>  char buf[10];
>  sprintf(buf, "%d", int_value);
>
>  write(0, buf, strlen(buf)-1);

strlen returns the number of characters in the string before the '\0' so
you don't want the -1. sprintf returns this value anyway so there's no
need to call strlen.

>A couple of points, this is not portable, why not use the stdio library,
>this would then become
>
>1)
>  printf("%*s", sizeof(int), (char*)&int_value);

No, %s outputs a string i.e. stops if it hits a '\0' which it may well
do within the internal representation of an integer. Also * reads an
int argument so you need (int)sizeof(int). A close standard equivalent is:

   fwrite(&int_val, sizeof(int), 1, stdout);

--
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Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
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