C Language Zemi

strrchr function-checks for characters from behind

Use the strrchr function to check from behind if a character is included. You can use the strrchr function by loading string.h.

#include <string.h>
char * strrchr (const char * string, int ch);

If string contains ch, it will search from the back and return the first matching address. If not found, returns NULL.

In C language, there is a promise that string ends with "\ 0". The strrchr function presupposes this convention and searches for a string.

When using the strrchr function, make sure that the string of the first argument ends with "\ 0".

Get the position where the character was found

This is a sample to get the position where the character is found by searching from the back with the strrchr function. Displays the position of the string where the last ":" is found.

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

int main (void) {
  const char * module_name = "Foo::Bar::Baz";
  
  // Get the address of the last ":"
  const char * match_ptr = strrchr (module_name,':');
  
  if (match_ptr! = NULL) {
    // Calculate the found position (relative position)
    int32_t match_index = match_ptr --module_name;
    
    printf("Match Position%d\n", match_index);
  }
  else {
    printf("Not Match\n");
  }
}

This is the output result.

Match Position 3