View Category
Files
Reading

Read the contents of a file into a string

scala
val text = FileUtils.readFileToString(new File("Solution467.scala"))
val text = Source.fromFile("Solution1256.scala").mkString("")
csharp
string contents = System.IO.File.ReadAllText("filename.txt");
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");

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
scala
val source = Source.fromFile(new File("Solution468.scala")).getLines
var n = 1 ; while (source.hasNext) { printf("%d> %s", n, source.next) ; n += 1 }
val source = Source.fromFile(new File("Solution469.scala")).getLines
for ((line, n) <- source zipWithIndex) { printf("%d> %s", (n + 1), line) }
csharp
int counter = 0;

// If the file is large, you would want to buffer this instead of reading everything at once
foreach (string line in System.IO.File.ReadAllLines("filename.txt"))
{
Console.WriteLine("{0}> {1}", ++counter, 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);
Writing

Write a string to a file

scala
FileUtils.writeStringToFile(new File("test.txt"), "This line overwites file contents!")
val fw = new FileWriter("test.txt") ; fw.write("This line overwites file contents!") ; fw.close()
csharp
System.IO.File.WriteAllText("filename.txt", "Some text to write to the file");
cpp
IO::StreamWriter^ stream;

try
{
stream = gcnew IO::StreamWriter("test.txt", false);
stream->WriteLine("This line overwites file contents!");
}

Append to a file

scala
val fw = new FileWriter("test.txt", true) ; fw.write("This line appended to file!") ; fw.close()
csharp
System.IO.File.AppendAllText("filename.txt", "Some text to append to the file");
cpp
IO::StreamWriter^ stream;

try
{
stream = gcnew IO::StreamWriter("test.txt", true);
stream->WriteLine("This line appended to file!");
}
Directories

Process each file in a directory

scala
for (file <- new File("c:\\").listFiles) { processFile(file) }
csharp
foreach (string filename in System.IO.Directory.GetFiles(directory)) ProcessFile(filename);
cpp
for each(String^ filename in IO::Directory::GetFiles(dirname)) process(filename);

Process each file in a directory recursively

scala
processDirectory(new File("c:\\"))
cpp
void processFile(String^ filename) { Console::WriteLine("{0}", filename); }

void processDirectory(String^ dirname)
{
for each(String^ filename in IO::Directory::GetFiles(dirname)) processFile(filename);
for each(String^ subdirname in IO::Directory::GetDirectories(dirname)) processDirectory(subdirname);
}

int main()
{
processDirectory("c:\\");
}