history命令如何仅将unix命令发送到用C编程的shell中的历史文件

Question

I have an assignment that requires me to create a history command, and I am stuck trying to figure out how the program would recognize that the input is a Unix command then send it to a file. If a user types junk, then it would not be sent to the history file; but if they type something like date , that would be sent to the history file.

Answer 1

You have to "look" into the environment variable PATH, and if the first word of the command correspond to a program that's inside the PATH, or (if it begin with a "/" and the program exist), you write that to the file. Good luck!