Question

I’m writing a program using Xcode for school that requires we use the open() system call. I do
int input_file_desc = open(input_path, O_RDONLY);
printf("input file desc %d:\n", input_file_desc);

and it comes up with a -1. The file’s path is ~/data_to_read. I set up the command line arguments in xcode. input_path is a const char * that i get from the command line. For some reason it works fine if I change the filename and command line argument to ~/data_to_read.txt. Let me know if more info is needed. thanks.

EDIT: I only tried it with .txt to see if that was the problem, but I still don’t know why it needs an extension in the first place. You can have files without an extension right? In which case it should still work, as long as neither the file path nor the argument has an extension, right?

Answer 1

It looks like you are using C, why the C++ tag then? is it allowed? there are easy and good classes in C++ to manipulate files.

However you definitely need to include the extension in the file name (the input_path) , as many files with the same name and different extensions can exist in the same directory, so which one should be opened?

EDIT: it should be known that file extensions are (especially in UNIX-Like OS) only a “helping” thing, they are not really essential. For Example, you could have a file that contains a C++ code but has no .cpp extension, for example its name is foo only with no extensions (or even has a crazy extension like foo.bar). Still you could use the g++ to compile it, because the extension is not really important as long as the content is valid for the application that uses that file.