c语言，多线程实现简单的终端处理器，读取文件，遇到特殊字符时采取相应操作

-A multi-threaded program using the pthread library.　Your assignment is to write a program that emulates a simple terminal handler.　The terminal handler process consists of three threads.　Thread 1reads characters from input.　In the input, some upper case letters represent control characters.　Each character read by thread 1 is passed onto thread 2 before another is read.　Thread 2 stores the characters as received.　However, the following four characters are control characters that ask thread 2 to take action accordingly.

　　B – erase last character from buffer

　　L – insert an end-of-line marker into buffer

　　C – remove contents of buffer

　　U – remove current incomplete line from buffer

The third thread, Thread 3, should read complete lines of characters (a line of character is complete, if it has an end-of-line character) from the buffer.　Thread 3 should then print this line.　Thread 2 should allow access only to completed lines in the buffer.　You may assume that a completed line