readfile.cs

/*
 * Read the contents of a file; optionally limit to X number of lines from the beginning of the file or Y number of lines from the end
 * 
 * USAGE: read.exe [+X] [-Y] <path_to_file>
 */

// To Compile:
//   C:\Windows\Microsoft.NET\Framework\v2.0.50727\csc.exe /t:exe /out:readfile.exe readfile.cs


using System;
using System.IO;

class ReadFile
{
    private static void PrintUsage()
    {
        string[] exePath = System.Diagnostics.Process.GetCurrentProcess().MainModule.FileName.Split('\\');
        string exeName = exePath[exePath.Length - 1];

        Console.WriteLine(@"Read the contents of a file; optionally limit to X number of lines from the beginning of the file or Y number of lines from the end

USAGE:
    {0} [+X] [-Y] <path_to_file>", exeName);
    }

    public static void Main(string[] args)
    {
        try
        {
            if (args.Length == 0)
            {
                PrintUsage();
                return;
            }

            int head = 0;
            int tail = 0;
            string filePath = "";
            int lineCount = 0;

            // Parse arguments
            for (int i = 0; i < args.Length; i++)
            {
                string arg = args[i];

                if (arg.StartsWith("+"))
                {
                    arg = arg.Replace("+", "");

                    bool test = int.TryParse(arg, out head);

                    if (test == false)
                    {
                        throw new ArgumentException("Invalid number of lines to read from head of file");
                    }
                }
                else if (arg.StartsWith("-"))
                {
                    arg = arg.Replace("-", "");

                    bool test = int.TryParse(arg, out tail);
                    if (test == false)
                    {
                        throw new ArgumentException("Invalid number of lines to read from head of file");
                    }
                }
                else
                {
                    filePath = arg;
                }
            }

            if (File.Exists(filePath))
            {
                // If tail is specified, determine line count
                if (tail > 0)
                {
                    using (StreamReader file = new StreamReader(filePath))
                    {
                        while (file.ReadLine() != null)
                        {
                            lineCount++;
                        }
                    }
                }

                // Use StreamReader so the entire files doesn't have to get read into memory at once
                using (StreamReader file = new StreamReader(filePath))
                {
                    int i = 0;
                    string line;

                    while ((line = file.ReadLine()) != null)
                    {
                        // Print the line if it's less than head, greater than tail, or neither head nor tail are specified
                        if ((head > 0 && i < head) || (tail > 0 && i >= lineCount - tail) || (head == 0 && tail == 0))
                        {
                            Console.WriteLine(line);
                        }

                        // Stop when head is reached if tail is not also specified (for efficiency)
                        if (head > 0 && i == head && tail == 0)
                        {
                            break;
                        }

                        i++;
                    }
                }
            }
            else
            {
                throw new Exception("File does not exist");
            }
        }
        catch (Exception e)
        {
            Console.Error.WriteLine("[-] ERROR: {0}", e.Message.Trim());
        }
        finally
        {
            Console.WriteLine("\nDONE");
        }
    }
}