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Files

Reading

Read the contents of a file into a string

ruby

file = File.new("Solution108.rb")
whole_file = file.read

cpp

IO::FileStream^ file; String^ buffer;

try
{
file = gcnew IO::FileStream("test.txt", IO::FileMode::Open);
buffer = gcnew String((gcnew IO::BinaryReader(file))->ReadChars(file->Length));
}

IO::StreamReader^ stream; String^ buffer;

try
{
stream = gcnew IO::StreamReader("test.txt");
buffer = stream->ReadToEnd();
}

String^ buffer = IO::File::ReadAllText("test.txt");

clojure

(slurp "/tmp/foobar")

fsharp

let file = new FileStream("test.txt", FileMode.Open)
let buffer = new String((new BinaryReader(file)).ReadChars(Convert.ToInt32(file.Length)))

let stream = new StreamReader("test.txt")
let buffer = stream.ReadToEnd()

let buffer = File.ReadAllText("test.txt")

Process a file one line at a time

Open the source file to your solution and print each line in the file, prefixed by the line number, like:
1> First line of file
2> Second line of file
3> Third line of file

ruby

File.open("Solution103.rb").each_with_index { |line, count|
puts "#{count} > #{line}
}

cpp

IO::StreamReader^ stream; String^ ln; int i = 0;

try
{
stream = gcnew IO::StreamReader("test.txt");
while ((ln = stream->ReadLine())) Console::WriteLine("{0}> {1}", ++i, ln);
}

int i = 0;
for each(String^ line in IO::File::ReadAllLines("test.txt")) Console::WriteLine("{0}> {1}", ++i, line);

clojure

(defn read-line-by-line [fn]
(reduce str (map (partial format "%d> %s\n")
(iterate inc 1)
(read-lines fn))))

fsharp

let stream = new StreamReader("test.txt")
let mutable i = 1
let mutable line = stream.ReadLine()
while (line <> null) do printfn "%d> %s" i line ; line <- stream.ReadLine() ; i <- i + 1 done
stream.Close()

let proc_a_line (filename : string) proc =
let stream = new StreamReader(filename)
let rec proc_a_line' count line =
match line with
| null -> stream.Close()
| _ -> proc count line ; proc_a_line' (count + 1) (stream.ReadLine())
proc_a_line' 1 (stream.ReadLine())

// ------

let _ = proc_a_line "test.txt" (fun i line -> printfn "%d> %s" i line)

let reader(filename : string) = seq {
use sr = new StreamReader(filename)
while not sr.EndOfStream do
let line = sr.ReadLine()
yield line
done
}

// ------

reader("test.txt") |> Seq.iteri (fun i line -> printfn "%d> %s" (i + 1) line)

File.ReadAllLines("test.txt") |> Array.iteri (fun i line -> printfn "%d> %s" (i + 1) line)

// Unlike ReadAllLines, ReadLines (new in .NET 4) only reads the file
// one line at a time, rather than reading the entire file into an array first.

open System.IO
File.ReadLines("test.txt") |> Seq.iteri (fun i line -> printfn "%d> %s" (i + 1) line)