Small D program to do some stuff with a file.

fileAppend.d

/*
 * Pseudocode
 * Read Infomation on what needs to happen from the user
 * Open file
 * Read each line of the file to an array of strings
 * Apply operations to array of strings
 * Write each element of the array to the file
 * 
 * Syntax:
 * Arguments go in this order: Input File, Output file, Prefix, Suffix
 * 
 */

import std.stdio, std.file, std.string;

/*
string readString (string text) {
	string stringOut;
	
	writeln(text);
	string output = strip(readln());
	
	return stringOut;
}*/

int main(string[] args) {
	
	File inFile, outFile;
	string inLine;
	/*
	string prefix = readString("What do you want before each line of the file? ");
	string suffix = readString("What goes at the end of each line?");
	string input =  readString("What file do we apply this operation to?");
	string output = readString("What file do we dump this operation to?");*/
	
	string input = args[1];
	string output = args[2];
	string prefix = args[3];
	string suffix = args[4];
	
	try {
		inFile = File(input, "r");
	} catch (std.exception.ErrnoException) {
		writeln("We can't read that file!");
		return 1;
	}
	outFile = File(output, "w");
	
	while (!inFile.eof()) {
        inLine = strip(inFile.readln());
        outFile.writeln(prefix, inLine, suffix);
    }
	return 0;
}

You missed a change to name it Appen.d....