View Category
Files
Reading

Read the contents of a file into a string

perl
@file = read()
open(my $fh, '<', $path) or die "can't open $path: $!";
$string = do { local $/; <$fh> };
close $fh;
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");
csharp
string contents = System.IO.File.ReadAllText("filename.txt");
fantom
contents := File(`file.text`).readAllStr

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
perl
open(my $fh, '<', $path) or die "can't open $path: $!";
$c = 1;
print $c++ . "> $_" for (<$fh>);
close $fh;
open my $fh, '<', $path or die "Can't open $path: $!";
while (<$fh>) {
print "$.> $_";
}
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);
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);
}
fantom
File(`input.text`).readAllLines.each |Str s, Int i| { echo("${i+1}> $s") }
Writing

Write a string to a file

perl
open(my $fh, '>', $path) or die "can't open $path: $!";
print $fh "This line overwites file contents!";
close $fh;
cpp
IO::StreamWriter^ stream;

try
{
stream = gcnew IO::StreamWriter("test.txt", false);
stream->WriteLine("This line overwites file contents!");
}
csharp
System.IO.File.WriteAllText("filename.txt", "Some text to write to the file");
fantom
File(`out.txt`).out.writeChars("some text").flush

Append to a file

perl
open(my $fh, '>>', $path) or die "can't open $path: $!";
print $fh "This line is appended to the file!";
close $fh;
cpp
IO::StreamWriter^ stream;

try
{
stream = gcnew IO::StreamWriter("test.txt", true);
stream->WriteLine("This line appended to file!");
}
csharp
System.IO.File.AppendAllText("filename.txt", "Some text to append to the file");
fantom
File(`out.txt`).out(true).writeChars("some text").flush
Directories

Process each file in a directory

perl
use File::Glob;

for (<*>) {
process_file($_) if (-f);
}
cpp
for each(String^ filename in IO::Directory::GetFiles(dirname)) process(filename);
csharp
foreach (string filename in System.IO.Directory.GetFiles(directory)) ProcessFile(filename);
fantom
File(`./`).list.each { process(it) }

Process each file in a directory recursively

perl
use File::Glob;

process_directory(".");

sub process_directory {
my $dir = shift;
for my $file (<$dir/*>) {
next unless (-r $file);
if (-f $file) {
process_file($file);
} elsif (-d $file) {
process_directory($file);
}
}
}
use File::Find ();

# Traverse desired filesystems
sub process_directory {
my $directory = shift;
File::Find::find({wanted => \&wanted}, $directory);
}

sub wanted {
process_file( $File::Find::name );
}
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:\\");
}
fantom
File(`./`).walk { process(it) }