Parse an HTTP status line

Challenge

Reading a banner from a local service often means parsing its first response line. For HTTP, extract the status code:

int parse_http_status(const char *resp);

Return the 3-digit status code from a line like "HTTP/1.1 200 OK", or −1 if the line does not start with "HTTP/" or has no valid 3-digit code.

Input format

A NUL-terminated response line.

Output format

The status code, or −1.

Constraints

The line must begin with HTTP/. The code is the first space-delimited token and must be exactly three digits.

Starter code

#include <stddef.h>
/* A local service replied with an HTTP status line like "HTTP/1.1 200 OK".
   Return the 3-digit status code (100..599 range not enforced beyond 3 digits),
   or -1 if the line does not start with "HTTP/" or has no valid 3-digit code. */
int parse_http_status(const char *resp){ (void)resp; return -1; }

Common mistakes

Not checking the HTTP/ prefix; reading fewer/more than three digits; accepting a code not delimited by a space/CR/LF/end.

Edge cases to handle

"HTTP/1.1 200 OK"→200; "HTTP/1.1 2 OK" and "200 OK" are invalid; the code may end the string.