字符串长度

#include <stdio.h>#include <stdlib.h>size_t strrlen(char *string){  int len = 0;  while(*string++ != '\0')        len++;  return len;}int main(int agrc,char **argv){  char *scan;  int len = 0;  if(argv[1] == NULL){        printf("Usage: %s [ char ] \n",argv[0]);        exit (0);  }  scan = argv[1];  len = strrlen(scan);  printf("len = %d\n",len);}