includes `strdup()` and `strndup()`
`strndup()` follows the latest standard, meaning that it copies at most _n_ chars, not _n_ + 1.
-also, no standard specifies that `strndup()` should return less than _n_ if `strlen(s) + 1` < _n_, but this implementation does so.
+Also, no standard specifies that `strndup()` should return less than _n_ if `strlen(s) + 1` < _n_, but this implementation does so.
---
### strlcat
includes `strlcat()` and `strlcpy()`
+
+---
+
+### strtonum
+
+includes `strtonum()`