linux open returns 0

Question

The code is like this:

int fd = open(filename, O_RDONLY);

"max open files" is 1024. The process may opened hundreds of files. At the beginning, it works good. After a while, open returns 0. I don't know why. Help!!! Thanks advance!

ps: It's not int fd = open(filename, O_RDONLY) == -1;

Answer 1

When open returns 0, it's telling you that you should use fd 0 if you want to use the file you just opened.

Did you perchance close stdin?