I/O

File I/O

High-Level Functions

import io.file

Function	Signature	Description
`readText`	`(path: String) r: String`	Read entire file to string
`writeText`	`(path: String, content: String) r: Bool`	Write string to file
`appendText`	`(path: String, content: String) r: Bool`	Append string to file
`exists`	`(path: String) r: Bool`	Check if file exists
`deleteFile`	`(path: String) r: Bool`	Delete a file
`createDirectory`	`(path: String) r: Bool`	Create a directory
`ensureParentDirectories`	`(path: String) r: Bool`	Create parent directories needed for a file path
`writeLines`	`(path: String, lines: Array<String>) r: Bool`	Write lines with newline separators
`size`	`(path: String) r: Int`	Return file size, or `-1` on failure
`hash`	`(path: String) r: String`	Return a stable file-content hash string

Example

let content = readText("config.toml")
println("Config: {content}")

writeText("output.txt", "Hello, World!")

FsFile Class

For more control over file operations:

let file = FsFile.open("data.txt")
let content = file.readContent()
file.closeFile()

Method	Return	Description
`open(path: String)`	`FsFile`	Open for reading
`create(path: String)`	`FsFile`	Open for writing (create/truncate)
`readContent()`	`String`	Read all content
`read_bytes(size: Int)`	`Array<Int>`	Read N bytes
`writeContent(content: String)`	`Void`	Write string
`write_bytes(data: Array<Int>)`	`Void`	Write bytes
`closeFile()`	`Void`	Close file
`size()`	`Int`	Get file size

FsFileResult represents file-open/read outcomes that need to carry success state alongside file data or errors.

Runtime File Functions

Function	Description
`__OpenFile(path, mode)`	Open file, return fd (-1 on error)
`__ReadFile(fd)`	Read entire content
`__ReadFileBytes(fd, size)`	Read N bytes
`__WriteFile(fd, content)`	Write string
`__WriteFileBytes(fd, bytes)`	Write byte array
`__CloseFile(fd)`	Close file descriptor
`__FileSize(fd)`	Get file size
`__FileError(fd)`	Get error message
`__FileExists(path)`	Check existence
`__DeleteFile(path)`	Delete file
`__CreateDirectory(path)`	Create directory

Standard I/O

Output

Function	Description
`println(s: String)`	Print string with newline
`__Print(s: String)`	Print without newline
`__PrintInt(n: Int)`	Print integer
`__PrintFloat(f: Float)`	Print float
`__PrintRaw(s: String)`	Print without newline (for LSP headers)
`__FlushStdout()`	Flush stdout buffer

Input

Function	Description
`__ReadStdinLine()`	Read one line from stdin (blocking)
`__ReadStdinBytes(count: Int)`	Read exactly N bytes from stdin

StdinReader Class

import io.stdio

Method	Return	Description
`nextLine()`	`String`	Read next line
`isEof()`	`Bool`	Check end of input

ContentLengthReader

For LSP/JSON-RPC message framing:

let reader = ContentLengthReader.new()
let message = reader.readMessage()
let err = reader.getLastError()

Buffered I/O

import io.buffered

BufferedWriter -- buffered output

BufferedReader -- buffered input

Path Operations

import fs.path

Function	Signature	Description
`isAbsolute`	`(path: String) r: Bool`	Check absolute path
`normalize`	`(path: String) r: String`	Normalize path
`join`	`(parts: Array<String>) r: String`	Join path components
`basename`	`(path: String) r: String`	Get filename
`dirname`	`(path: String) r: String`	Get directory
`pathExtension`	`(path: String) r: String`	Get file extension
`withoutExtension`	`(path: String) r: String`	Remove extension
`splitComponents`	`(path: String) r: Array<String>`	Split into components

Example

let full = join(["home", "user", "docs", "file.txt"])
let dir = dirname(full)       // "home/user/docs"
let file = basename(full)     // "file.txt"
let ext = pathExtension(full) // "txt"