text: #ifndef MYSTRING_H
  #define MYSTRING_H
  
  #include <stddef.h>	//included to use size_t
  
  int atoi(const char *nptr);
  long atol(const char *nptr);
  
  size_t strlen(const char *s);
  
  char *strcpy(char *dest, const char *src);
  char *strncpy(char *dest, const char *src, size_t n);
  
  char *strcat(char *dest, const char *src);
  char *strncat(char *dest, const char *src, size_t n);
  
  char *strdup(const char *str);
  
  int strcmp(const char *s1, const char *s2);
  int strncmp(const char *s1, const char *s2, size_t n);
  
  char *strchr(const char *s, int c);
  char *strrchr(const char *s, int c);
  char *strstr(const char *haystack, const char *needle);
  
  char *strtok(char *str, const char *delim);
  char *strtok_r(char *str, const char *delim, char **saveptr);
  
  #endif
  