一个自编的读取文本文件数据的函数，可以读取整个文件，读取第N行，读取第M行到第N行，读取第M行到倒数第N行，读取第M次（也可以是最后一次、倒数第M次）出现字符串str的行开始（或结束）的数据，等等。希望能给大家带来帮助！

-A self-read text file data function, you can read the entire document, read the first N lines, M reads the first line to the first N lines, M reads the first line to the penultimate N line, read the first M sub- (can also be the last, the penultimate meeting M) of the line str string start (or end) of the data, and so on. I hope everyone can help!