mkfifo() error ---> “Error creating the named pipe.: File exists”

Question

The mkfifo function takes 2 arguments, path and mode. But I don't know what is the format of the path that it uses. I am writing a small program to create a named pipe and as path in the mkfifo. Using /home/username/Documents for example, but it always returns -1 with the message Error creating the named pipe.: File exists.

I have checked this dir a lot of times and there is no pipe inside it. So I am wondering what is the problem. The mode I use in mkfifo is either 0666 or 0777.

Answer 1

You gave mkfifo() the name of an existing directory, thus the error. You must give it the name of a non-existing file, e.g.

mkfifo("/home/username/Documents/myfifo", 0600);

Answer 2

The 'path' argument to mkfifo() has to specify a full path, the directory and the filename that is.

Thus, it would be:

char *myfifo="/home/username/Documents/mypipe";

mkfifo(myfifo, 0777);

As a side note, you should avoid using octal permission bits and use named constants instead (from sys/stat.h), so:

mkfifo(myfifo, S_IRWXU | S_IRWXG | S_IRWXO);