Standard Library: File

The file module provides high-level filesystem operations for reading and writing text files. All operations go through a filesystem provider, which means they work transparently with sandboxed and virtual filesystems.

For lower-level I/O (handles, seeking, raw bytes, network, processes), see Standard Library: I/O.

Importing

from std::core::file use { read_text, write_text, read_lines, append }

Functions

file::read_text

Read the entire contents of a file as a UTF-8 string.

let content = file::read_text("config.toml")?
print(content)

file::write_text

Write a string to a file, creating it if it does not exist or truncating it if it does.

file::write_text("output.txt", "Hello, Shape!")?

file::read_lines

Read a file and return its lines as an array of strings.

let lines = file::read_lines("data.csv")?
for line in lines {
    print(line)
}

file::append

Append a string to a file, creating it if it does not exist.

file::append("log.txt", "new log entry\n")?

Function Reference

Function	Signature	Description
file::read_text(path)	(string) -> Result<string, string>	Read file as UTF-8 string
file::write_text(path, content)	(string, string) -> Result<(), string>	Write string to file
file::read_lines(path)	(string) -> Result<Array<string>, string>	Read file as array of lines
file::append(path, content)	(string, string) -> Result<(), string>	Append string to file

Working With Bytes

The file module exposes only text-level operations. To read or write raw byte arrays, use the io module’s handle-based API:

use std::core::io

let f = io::open("image.png", "r")
let bytes = io::read_bytes(f, 1024)
// f auto-closes when it goes out of scope

See Standard Library: I/O for the full handle-based API including io::read_bytes, io::write, and async variants like io::read_file_async, io::read_bytes_async.

Permissions

Read operations (read_text, read_lines) require the FsRead permission. Write operations (write_text, append) require the FsWrite permission. See Security & Permissions for details.

See Also

• Standard Library: I/O — lower-level I/O with handles, seeking, raw bytes, network, and processes
• Security & Permissions — filesystem permission gating