一些字符串函数的用法

strnpy:   https://blog.csdn.net/sinat_30071459/article/details/72771137

strncat:  https://blog.csdn.net/sky2098/article/details/1530662

strchr:    https://blog.csdn.net/github_33736971/article/details/51952453

strrchr:

strstr:    https://blog.csdn.net/ludaoyi88/article/details/52819448

strpbrk: https://blog.csdn.net/tommy_wxie/article/details/7554332

strspn:  https://blog.csdn.net/ubuntulover/article/details/18838613

strcspn: