2.2.19 size_t strcspn
size_t strcspn(const char *__s, const char *__reject) __ATTR_PURE__
The strcspn() function calculates the length of the initial segment of s
which consists entirely of characters not in reject
.
Remember:
The strcspn() function returns the number of characters in the initial segment of s
which are not in the string reject
. The terminating zero is not considered as a part of string.