IO

The @std/io module provides console input, file streams, and file writing.

import io from "@std/io"

let name = io.read("Name: ")

println("Hello", name)

Exports

Name	Kind	Description
Stream	struct	Stream returned by io.open.
read	function	Reads text from standard input.
open	function	Opens a file as a stream.
writeFile	function	Writes data to a file.

io.read

Reads a string from standard input.

Arguments:

Name	Type	Default	Description
text	string	""	Prompt text printed before reading.
trim	bool	true	Whether to trim surrounding whitespace.
endln	char	'\n'	Character that ends input.

Returns: string

import io from "@std/io"

let name = io.read("Name: ")

println(name)

Read without trimming:

import io from "@std/io"

let raw = io.read("Raw: ", false)

println(raw)

io.open

Opens a file and returns a Stream.

Arguments:

Name	Type	Default	Description
file	string	none	File path.
mode	string	"r"	Open mode.
perm	int	system default	File permissions for created files.
encoding	string	"utf-8"	Text encoding.

Returns: Stream

import io from "@std/io"

let stream = io.open("README.md")

println(stream.readAll())

stream.close()

Relative paths are resolved from the current source file when debug file information is available.

Open Modes

Mode	Description
"r"	Read-only. File must exist.
"r+"	Read/write. File must exist.
"rw"	Read/write. File must exist.
"w"	Write-only. Create or truncate.
"w+"	Read/write. Create or truncate.
"rw+"	Read/write. Create or truncate.
"a"	Write-only append. Create if needed.
"a+"	Read/write append. Create if needed.

Encodings

Supported encodings:

Name
utf-8
utf-16
utf-16le
utf-16be
latin1
iso-8859-1
windows-1252
cp1252

io.writeFile

Writes data to a file.

Arguments:

Name	Type	Default	Description
file	string	none	File path.
data	any	none	Data to write. Converted to string.
perm	int	system default	File permissions.

import io from "@std/io"

io.writeFile("hello.txt", "Hello, Nubo")

Stream

A Stream supports reading, writing, and closing depending on how it was opened.

Reading Methods

Method	Returns	Description
read()	string	Reads up to a chunk of data.
readAll()	string	Reads the rest of the stream.
readByte()	byte	Reads one byte.
readLine()	string	Reads one line without the trailing newline.
readLines()	[]string	Reads lines into a list.

import io from "@std/io"

let stream = io.open("notes.txt")

println(stream.readLine())
println(stream.readAll())

stream.close()

Writing Methods

Writing methods are available when the stream was opened in a writable mode.

Method	Returns	Description
write(content)	int	Writes a string and returns bytes written.
writeByte(content)	int	Writes one byte and returns bytes written.

import io from "@std/io"

let stream = io.open("out.txt", "w")

stream.write("Hello")
stream.writeByte(byte(10))
stream.write("Nubo")

stream.close()

Closing

Always close streams when finished.

import io from "@std/io"

let stream = io.open("out.txt", "w")

stream.write("done")
stream.close()