Thread: If someone could explain.

Why does this print 1, I thought it should print 0 since there is nothing in it and strlen dosn't count the \0 at the end of the string.

Code:

#include <stdio.h>
#include <string.h>

int main () {
    char a[50];
    int b = strlen(a);
    printf("\nlength:%d\n",b);
    
   return(0);
}

Now here

Code:

#include <stdio.h>
#include <string.h>

int main()
{
    char a[50];
    int b = strlen(a);
    printf("\nlength:%d\n",b);
       
    a[0]=fgetc(stdin);
    printf("\n--%c\n",a[0]);
    b = strlen(a);
    printf("\nlength:%d\n",b);
    
    a[0]=0;
    printf("\n--%c\n",a[0]);
    b = strlen(a);
    printf("\nlength:%d\n",b);
    
}

but not looking at this part

Code:

int main()
{
    char a[50];
    int b = strlen(a);
    printf("\nlength:%d\n",b);

I give the char a[0] a character, and then I say that the value of a[0] is [NULL].

And then it dosnt see anything there.

So for example if I had a string and use fgets and stdin to write in it, and then for every character of the char string I say it equals to 0, that is [NULL].

So then it would show me strlen 0, and it wold look as if the string is empty.
Why is that so btw?


Oh and another question my friend told me if I do this

char text[500] = {0};

That then basicly every char should be = 0;
Is that really how it works?

Because your strings are uninitialised, so strlen() could be anything.

> Is that really how it works?
Yes.

Originally Posted by jimblumberg

And note in many circumstances NULL is defined as ((void *)0) which doesn't always evaluate to zero.

I think that is false: ((void *)0) always evaluates to zero, even if the internal representation might not actually be a representation for zero. This must be so because in the condition of an if statement, the decision as to whether to execute the body of the if statement depends on whether the expression compares unequal to 0. If ((void *)0) does not evaluate to zero, then we have a case where a null pointer as the expression of an if statement's condition causes the if statement's body to be executed.