file_streams's Introduction

Gleam File Streams

This Gleam library provides access to Erlang's file streams for reading and writing files. If you don't require streaming behavior then consider using simplifile instead.

This library only supports the Erlang target.

Example

Add this library to your project:

gleam add file_streams

The following code writes data to a file using a write stream, reads it back in using a binary file stream, then reads it again with a text file stream.

import file_streams/read_stream
import file_streams/read_stream_error
import file_streams/read_text_stream
import file_streams/write_stream
import gleam/bit_array

// Write file
let assert Ok(ws) = write_stream.open("test.txt")
let assert Ok(Nil) = write_stream.write_string(ws, "Hello, world!\n")
let assert Ok(Nil) = write_stream.write_bytes(ws, <<"12":utf8>>)
let assert Ok(Nil) = write_stream.close(ws)

// Read file as a binary stream
let assert Ok(rs) = read_stream.open("test.txt")

let assert Ok(bytes) = read_stream.read_bytes(rs, 14)
let assert Ok("Hello, world!\n") = bit_array.to_string(bytes)
let assert Ok([49, 50]) = read_stream.read_list(rs, read_stream.read_uint8, 2)
let assert Error(read_stream_error.EndOfStream) = read_stream.read_bytes(rs, 1)

let assert Ok(Nil) = read_stream.close(rs)

// Read file as a text stream so UTF-8 characters and lines can be read
let assert Ok(rts) = read_text_stream.open("test.txt")

let assert Ok("Hello") = read_text_stream.read_chars(rts, 5)
let assert Ok(", world!\n") = read_text_stream.read_line(rts)
let assert Ok("12") = read_text_stream.read_line(rts)
let assert Error(read_stream_error.EndOfStream) = read_text_stream.read_line(rts)

let assert Ok(Nil) = read_text_stream.close(rts)