How to check if string starts with certain string in C?

Question

For example, to validate the valid Url, I\'d like to do the following

char usUrl[MAX] = \"http://www.stackoverflow\"

if(usUrl[0] == \'h\'
   && usUr         


        

Answer 1

strstr(str1, "http://www.stackoverflow") is another function that can be used for this purpose.

Answer 2

A solution using an explicit loop:

#include <stdio.h>
#include <stddef.h>
#include <stdbool.h>

bool startsWith(const char *haystack, const char *needle) {
    for (size_t i = 0; needle[i] != '\0'; i++) {
        if (haystack[i] != needle[i]) {
            return false;
        }
    }

    return true;
}

int main() {
    printf("%d\n", startsWith("foobar", "foo")); // 1, true
    printf("%d\n", startsWith("foobar", "bar")); // 0, false
}

Answer 3

The following should check if usUrl starts with "http://":

strstr(usUrl, "http://") == usUrl ;

Answer 4

bool StartsWith(const char *a, const char *b)
{
   if(strncmp(a, b, strlen(b)) == 0) return 1;
   return 0;
}

...

if(StartsWith("http://stackoverflow.com", "http://")) { 
   // do something
}else {
  // do something else
}

You also need #include<stdbool.h> or just replace bool with int

Answer 5

I would suggest this:

char *checker = NULL;

checker = strstr(usUrl, "http://");
if(checker == usUrl)
{
    //you found the match

}

This would match only when string starts with 'http://' and not something like 'XXXhttp://'

You can also use strcasestr if that is available on you platform.