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-   -   Something Loopy in Assigning Strings (http://www.go4expert.com/showthread.php?t=6393)

MattFunke 17Sep2007 18:03
Something Loopy in Assigning Strings
 
I tried this in desperation after strcat() refused to work. I just want to concatenate three strings. Can anyone tell me why this doesn't work? I can see the creation of "10", but not of "11", though there's plenty of room on the disk for both. Moreover, if I ask for a printf of fieldn and strlen(fieldn) for all three fields, I get the right responses. field1[] is more than long enough to handle the job.

Code:
void AssembleData(char field1[], char field2[], char field3[])
{
    int i;
    int startPos;
    int stopPos;

    if (field2[0] != '\0')
    {
        startPos = strlen(field1);
        stopPos = startPos + strlen(field2);

        system("touch /var/log/10\n");

        for (i = startPos; i < stopPos; i++)
        {
            field1[i] = field2[i - startPos];
        }

        system("touch /var/log/11\n");

        if (field3[0] != '\0')
        {
            startPos += strlen(field2);
            stopPos += strlen(field3);

            for (i = startPos; i < stopPos; i++)
            {
                field1[i] = field2[i - startPos];
            }
        }
    }
}

DaWei 17Sep2007 18:20
Re: Something Loopy in Assigning Strings
 
That's just silly. Disk operations are orders of magnitude slower than memory operations. Use strcat or strncat. They work. If you can't get them to work, show THAT code not this grossly over-footprint, underperforming stuff.

MattFunke 17Sep2007 18:32
Re: Something Loopy in Assigning Strings
 
I explained in the first message that I tried strcat() and that it doesn't work, either. Here's the code. As usual, I can get "10" but not "11".

Code:
void AssembleData(char field1[], char field2[], char field3[])
{
    system("touch /var/log/10\n");

    field1 = strcat(field1, field2);
    field1 = strcat(field1, field3);

    system("touch /var/log/11\n");
}
I would appreciate any help you could lend, but I would also appreciate it if you could acknowledge the things that I've already mentioned I've tried without success.

MattFunke 17Sep2007 21:10
Re: Something Loopy in Assigning Strings
 
Found it! Here's the problem. This is what I was doing, essentially:

Code:
#define HI_THERE "hi "
#define ID10T "idiot"
char *data;

data = strcat(HI_THERE, ID10T);
... and the statement, of course, after the preprocessor was done with it, looked like this:

Code:
data = strcat("hi ", "idiot");
It was trying to concatenate literals, not string variables. This works:

Code:
char data[80] = HI_THERE;
char data2[80] = ID10T;

data = strcat(data, data2);
<dope slaps self>

DaWei 18Sep2007 00:14
Re: Something Loopy in Assigning Strings
 
Actually, the second string can be a literal. There MUST be enough storage in the destination string to accomodate the original plus the second string (literal or otherwise).


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