I started to write programs and found myself mentally retarded.

I forgot how to play C language. Faint ~
Now I am in a very impetuous mood, and I am too lazy to take a closer look at the document. As a result, today and yesterday's two problems are caused by the lack of clear descriptions of library functions.
I miss the convenience that msdn has given me, but I can't use it now. I am dizzy, looking for documents everywhere, and still haven't found official Linux or standard C language library materials.
It seems that everything should start from the beginning, become a primary school student, learn modestly, and practice carefully.
Segment fault, it's so disgusting ~