How do you use an if else and check for last character '\0' of a string?-CodePudding

In C apparently strings are stored like an array with a null value or '\0' at the end. I wish to iterate over the string in a for loop and I need it to stop at '\0', not including it. I've tried many conditions for the if else and it all don't seem to work.

for example:

char patternInput[TEXTSIZE];

for(int i = 0; i<strlen(patternInput);i  )
{
    if(patternInput[i]==NULL)
    {
        printf("\nlast character");
        break;
    }
    else
    {
        printf("\n%c",patternInput[i]);
    }
}

I've tried if(patternInput[i]==NULL), if(patternInput[i]==NUL),if(!patternInput[i]),if(patternInput[i]=='\0') and none of them seems to work.

CodePudding user response：

If you're scanning the characters yourself, you can avoid the (redundant and somewhat expensive) strlen() call entirely, and instead use the value of patternInput[i] in the continuation-test of your for-loop:

char patternInput[TEXTSIZE] = "testing!";

for(int i = 0; patternInput[i] != '\0'; i  )
{
   printf("\n%c",patternInput[i]);
}
printf("\nlast character\n");

CodePudding user response：

Consider this code. This code prints 'Null character found' with position of the character. Notice the 'less than or equal to' in i<=strlen(str) in the loop invariant.

The last character at the length strlen 1 is the '\0' character.

int i = 0;
    
char str[] = "Hello";
    
for(int i=0; i<=strlen(str); i  )
{
    if(str[i]=='\0')
        printf("Null character found at position %d", i);
}