Question

I am very new with c and less experienced with any other language :/
For an assignment at uni, I am a little stuck on this small part. Essentially I am required to write a ‘ls’ function that has 4 optional arguments, for example:

list [-l] [-f] [pathname] [localfile] 

Now, the first two are straight forward. To make things more difficult, the ‘localfile’ doesn’t necessarily exist and the ‘pathname'(if given) will be located on the server I’m connecting to through a socket (so checking if it is a file is out and checking the pathname is out). I was thinking, check last 4 chars in the string for a ‘.txt’ or something similar. I’m actually completely stumped and will present this problem to my course conveyor tomorrow, if I can’t find a solution.

This is a very small part of what I actually have to do but any push in the right direction would be appreciated.

Answer 1

You will need to process argc and argv to get your command line arguments. That is the first thing to work on, getting the arguments – ensuring they are correct, and determining what is being asked for.

int main(int argc, char  *argv[])

Assuming your are on Linux/Unix, you will need to use the directory functions opendir()/readdir()/closedir() – dirent.h. The stat() function will be required to satisfy the -l requirement. access() will determine if a file exists and then stat() will tell you if the file is a regular file or a directory.

I’d make a struct to hold the four optional arguments and return it from a function called “process_arguments” that takes argc and argv as parameters.

struct args {
  bool valid;
  bool l_option;
  bool f_option
  char directory[200]; 
  char filename[200];
}

With the requirement for a socket connection you will have to write a “server program” that will be constantly running on the server and a “client program” that it will fork to handle the requests from your local program. Try and locate examples of socket programs.

Another check for whether you have a path string or a filename is to look for the path separator character – ‘/’ if the server is Unix/Linux. This scheme shouldn’t have any path separators in filenames, so the presence of one tells you it is a path.