Date: Mon, 18 Feb 2008 17:41:42 -0600 From: Tim Daneliuk <tundra@tundraware.com> To: tundra@tundraware.com Cc: Gary Kline <kline@thought.org>, FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: is there an easier way? Message-ID: <47BA17B6.20906@tundraware.com> In-Reply-To: <47BA14F8.4060109@tundraware.com> References: <20080218230351.GA28000@thought.org> <47BA1375.2010108@tundraware.com> <47BA14F8.4060109@tundraware.com>
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Tim Daneliuk wrote:
> Tim Daneliuk wrote:
>> Gary Kline wrote:
>>> To my fellow C nerds,
>>>
>>> It's been a great manny years since I wrote this appended
>>> snippet. Now I can't remember why (of if ) I need all the
>>> strcpy() calls. Is there a simpler, more logical way of
>>> printing a bunch of string by snipping off the left-most?
>>>
>>> In short,, can anyone 'splain why strtok needs all this?
>>>
>>> tia,
>>>
>>> gary
>>>
>>>
>>
>> I don't think you need the copies. This works just as well:
>>
>> #include <stdio.h>
>> #include <string.h>
>>
>> main()
>> {
>> char *bp, *tok;
>> char *delim=" ", s1[256]="abc def ghi jkl mno.";
>>
>> bp = s1; /* Now both point to the literal string to be tokenized */
>>
>> while ((tok = strtok(bp, delim)) != NULL)
>> {
>> bp = NULL;
>> printf("tok = [%s]\n", tok);
>> }
>> }
>>
>
>
> Ooops ... wasn't paying attention. While the printed output is the
> same, doing
> it this way is destructive to the original s1 string - which may matter
> (or not)...
So, to protect the original string, you do have to copy the original
string to a new buffer:
#include <stdio.h>
#include <string.h>
main()
{
char *bp, *tok, buf[256];
const char *delim=" ", s1[256]="abc def ghi jkl mno.";
bp = strcpy(buf, s1);
while ((tok = strtok(bp, delim)) != NULL)
{
bp = NULL;
printf("tok = [%s]\n", tok);
}
}
So, at least we eliminated the first strcpy in your code:
char *bp, buf[512], *tok, tstr[512];
static char *delim=" ", s1[256]="abc def ghi jkl mno.";
bp = strcpy(buf, tstr);
This accomplishes nothing and may not even be safe - strcpy() copies
until it hits \0. I do not recall if the declaration of tstr[512]
intializes it to \0. If not, then the strcpy() is going to keep
running until it finds one, overwriting the end of buf[] and probably
causing core dumps or other evil...
--
----------------------------------------------------------------------------
Tim Daneliuk tundra@tundraware.com
PGP Key: http://www.tundraware.com/PGP/
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