Question

I’m currently learning the C language in college so this is a homework assignment but I have a small problem. I’m guessing I’ve just misjudged the syntax or are missing something really obvious. My compiler is telling me that there is:

expected declaration specifiers or “…” before constant

and pointing to the O_RDWR.

I’ve googled and searched on Stack Exchange but there doesn’t seem anything specific to it. Following the syntax in a C reference it’s fine. I’ve looked around and it says I have not predefined the typedef but I’ve tried that to no avail.

I’ve starred the section that is causing the problem according to the compiler with **

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

int main (int argc, char *argv[])
{
    int count;

    printf ("This program was called  \"%s\".\n",argv[0]);

    if (argc > 1)
    {
        for (count = 1; count < argc; count++)
        {
            printf("argv[%d] = %s\n", count, argv[count]);
        }
    }
    else
    {
        printf("The command had no arguments.\n");
    }

    if  (argc == 4)
    {
        printf("There are the correct number of arguments(4)");
    }
    else
    {
        printf("Not enough arguments! please try again");
    }

    **int open(const char *argv[1], O_RDWR);

    return 0;**
}

Answer 1

int open(const char *argv[1], O_RDWR); 

What are you trying to do by this statement? Compiler treats this as function declaration, not function call. And it fails because O_RDWR is not a type name. If you need to call open(), syntax shall be like this:

int fd = open(argv[1], O_RDWR);
if(fd != -1)
{
   // File opened OK. Proceed with file operations.
}
else
{
   // File failed to open. Handle error occured
}