FlexibleOpen

Using data files in CSC 1810 is hard if IDE's such as xcode or Visual Studio are used.

Visual Studio Code is somewhat easier as its users will be more likely to be shell users.

FlexibleOpen() attempts to ease the difficulty by adding a layer of indirection to the file opening process. Specifically, it attempts to open the file path given to it both as given and with a path, specified by environment variable, prepended.

Function signature

std::fstream FlexibleOpen(std::string path, std::ios::openmode mode = std::ios::in, std::string envval = std::string("CSC1810"));

Parameters

parameter	default	meaning
path	none	This specifies the base path of the file to be opened. If a file matching this path fails to open, the contents of an environment variable will be prepended to the path and a second open attempt is made.
mode	ios::in	The fstream mode for opening the file. This defaults to ios::in or attempting to open the file for reading.
envval	"CSC1810"	This specifies the environment variable to consult if the given path fails to open without change.

Use cases

Assume the environment variable is CSC1810 and on:

• Windows is set to ...
• Mac and Linux is set to ~/Documents/csc1810_files

Opening a file using all defaults

fstream fin = FlexibleOpen("data.txt");
if (fin.is_open()) {
	// Use the file... then close it.
	fin.close();
}

data.txt will be attempted for reading. If data.txt is not found in the current working directory, then ~/Documents/csc1810_files/data.txt will be attempted on Mac and Linux while ijijijij/data.txt will be attempted on Windows.

Opening a file for writing using default environment variable

fstream fin = FlexibleOpen("data.txt", ios::out);
if (fin.is_open()) {
	// Use the file... then close it.
	fin.close();
}

data.txt will be attempted for writing. If data.txt is not found in the current working directory, then ~/Documents/csc1810_files/data.txt will be attempted on Mac and Linux while ijijijij/data.txt will be attempted on Windows.

Opening a file for reading and writing using default environment variable

fstream fin = FlexibleOpen("data.txt", ios::in | ios::out);
if (fin.is_open()) {
	// Use the file... then close it.
	fin.close();
}

data.txt will be attempted for reading and writing. If data.txt is not found in the current working directory, then ~/Documents/csc1810_files/data.txt will be attempted on Mac and Linux while ijijijij/data.txt will be attempted on Windows.

Opening a file for reading using a different environment variable

fstream fin = FlexibleOpen("data.txt", ios::in, "OTHERVAR");
if (fin.is_open()) {
	// Use the file... then close it.
	fin.close();
}

data.txt will be attempted for writing. If data.txt is not found in the current working directory, then the value of environment variable OTHERVAR will be prepended and the open attempted again.

Creating the envronment variable

Mac and Linux

Suppose you create a directory in your Documents folder called csc1810_files. You place your data files for class in that folder.

Then add:

export CSC1810=/Users/YOURACCOUNT/Documents/csc1810_files

to .zshrc on newer macs, or to .bashrc on Linux.

Windows

Suppose you create a directory in your Documents folder called csc1810_files. You place your data files for class in that folder.

Use the Windows environment variable editor GUI to define the variable.

See the video here.

xcode idiocy

The whole point of creating this tool was to make it easier to use files in IDE-based projects. The geniuses at Apple once again, "think different." xcode actively blocks environronment variables forcing you to reenter them yourself inside xcode.

Edit scheme choose the Run / Debug scheme. Click the Arguments tab. Click the plus sign under Environment Variables then enter for Name: CSC1810 and for Value /Users/YOURACCOUNT/Documents/csc1810_files.