Using mknod on Ubuntu in c program

Question

I am trying to make a c program where i am using mknod command like

#include<stdio.h>
#include<fcntl.h>
#include<string.h>

char info[50];

main() {
    int fdr;
    int rc = mknod("testfile",'b',0);
    if(rc<0) {
        perror("Error in mnod");
    }
    fdr=open("testfile",O_RDONLY);
    read(fdr,info,50);
    printf("\n Received message=%s",info);
    printf("\n");
} 

And do some stuff. It works well on Red Hat system, but fails on ubuntu giving error invalid argument.

Solution 1

mknod is deprecated; you should not be using it. If you want to create a FIFO, use the standard mkfifo. If you want to create an ordinary file, use creat or open with O_CREAT. Yes mknod can create device nodes, and on some systems might still be the way to do it, but on a modern Linux system you rely on the kernel and/or udevd to handle this.

Solution 2

mknod("testfile",'b',0);

'b' is not a very sensible argument for mknod here. mknod's argument should be a bitwise OR of a permissions mask (modified by umask) and S_IFREG (for a regular file) or S_IFIFO (for a FIFO). For example:

mknod("textfile", S_IFREG | 0666, 0);