How to check if C string is empty

Question

I'm writing a very small program in C that needs to check if a certain string is empty. For the sake of this question, I've simplified my code:

#include <stdio.h> #include <string>  int main() {   char url[63] = {'\0'};   do {     printf("Enter a URL: ");     scanf("%s", url);     printf("%s", url);   } while (/*what should I put in here?*/);    return(0); } 

I want the program to stop looping if the user just presses enter without entering anything.

Answer 1

Since C-style strings are always terminated with the null character (\0), you can check whether the string is empty by writing

do {    ... } while (url[0] != '\0'); 

Alternatively, you could use the strcmp function, which is overkill but might be easier to read:

do {    ... } while (strcmp(url, "")); 

Note that strcmp returns a nonzero value if the strings are different and 0 if they're the same, so this loop continues to loop until the string is nonempty.

Hope this helps!

Answer 2

If you want to check if a string is empty:

if (str[0] == '\0') {     // your code here }