The strspn () function in C
function size_t strspn (const char * str1, const char * str2) calculates the length of the first character segment of the str1 string containing the characters in str2The strtok () function in C
char * strtok function (char * str, const char * delim) divides the string str into a sequence of tokens separately separated by delim separators (eg comma, ...).