Thread: Expecting a null character, but receiving a blank character instead

Consider the following declaration:

Code:

char error_msg[15] = "";

I call a function which essentially populates this error message with either an error message (in the case of an error), or with SPACES (if no error is encountered). For reasons I don´t need to get into in this post, I trim the string if it is returned to me as SPACES.
In the relevant section of the code, I check for its length:

Code:

printf("Length of error_msg = %d\n", strlen(error_msg));

When the error message comes back as spaces, the result of trimming the string and executing the line above is always 0. I interpret that to mean that the array is empty, and that the first element of the array is a null character (\0).
But the string compare below always returns a 32:

Code:

compare_result = strcmp(error_msg, "")

So I decided to do a printf to check the first element of the error message array:

Code:

printf("First element of the error msg array: %d", error_msg[0]);

I print the character as an integer in order to see the decimal 0, which corresponds to the null character. But the result I get is the decimal 32, which corresponds to the "blank space" character. Now, if there is a blank character as the first array element, shouldn´t the array length be GREATER than 0?

I think there´s something I´m missing here...
Thanks

strlen definitely should be counting leading spaces. A scope error (you having two variables called error_msg) is possible, especially if you're trying to cheat by using global variables. Can you give us a complete, compilable example that does bad things (rather than a line here and a line there)?

Originally Posted by AndrewHunter

No, by definition when you make the string literal you are making, aka

Code:

 char error_msg[15] = ""

, the string will contain the space character.

Pretty sure this is completely false (and probably irrelevant, given the description). Easy test:

Code:

#include <stdio.h>
int main(void) {
    char error_msg[15] = "";
    int i;
    for (i = 0; i < 15; i++) {
        printf("%d\n", error_msg[i]);
    }
    return 0;
}

I typed that straight into this box and didn't run it, but I'll bet you get a bunch of 0.

Originally Posted by AndrewHunter

You know what, scratch completely what I said. You are right Quzah. I don't even know what I was thinking.

... and thanks to that voltage reduction on your crystal ball, neither do I...

If Microsoft is involved the OP story could be true.

In MS T-SQL version 6.5 and empty string had a single space in it.

Tim S.

Andrew: Yup, as Quzah implied, "" has no blank space, as it´s the empty string. And as the definition goes, "An empty string is a character array with the NULL character in the zeroth index position".

Tabstop: No scope errors and no global variables. This error_msg is the only one there is. And yup, just as you predicted, we get all zeros when executing your program.

When I get err_msg fully populated by blank spaces (when there are no errors), I said that I call a trimming function. Here it is, just for the sake of it:

Code:

void RTRIM (char * chain)                                      
{
        long n;         /* Counter */
        for (n = strlen (chain); n > 0 && chain [--n] == ' '; chain [n] = '\0');
}

Again, after I call RTRIM, I call strlen to check the size of err_msg. The result I get is zero. Strlen returns the number of characters between the beginning of the string and the null character. So if the size I get back is 0, then the null character (\0 or 0 in decimal) must be the 0th element of the array, no? And if so, why in the world am I getting the decimal 25 (corresponding to a blank character) when I do the string compare below?

Code:

compare_result = strcmp(error_msg, "");

I confess I´m perplexed!!