fs

The fs module provides file system operations. Requires import fs. All functions are effect fn.

Function Reference

Reading

Function	Signature	Description
read_text	(String) -> Result[String, String]	Read file as UTF-8 string
read_bytes	(String) -> Result[List[Int], String]	Read file as byte list
read_lines	(String) -> Result[List[String], String]	Read file as list of lines

Writing

Function	Signature	Description
write	(String, String) -> Result[Unit, String]	Write string to file (create/overwrite)
write_bytes	(String, List[Int]) -> Result[Unit, String]	Write bytes to file
append	(String, String) -> Result[Unit, String]	Append string to file

Directory Operations

Function	Signature	Description
mkdir_p	(String) -> Result[Unit, String]	Create directory and parents
list_dir	(String) -> Result[List[String], String]	List directory entries
walk	(String) -> Result[List[String], String]	Recursively list all files
glob	(String) -> Result[List[String], String]	Find files matching glob pattern

File Queries

Function	Signature	Description
exists	(String) -> Bool	Check if path exists
is_file	(String) -> Bool	Check if path is a regular file
is_dir	(String) -> Bool	Check if path is a directory
is_symlink	(String) -> Bool	Check if path is a symlink
file_size	(String) -> Result[Int, String]	Get file size in bytes
modified_at	(String) -> Result[Int, String]	Get modification time (Unix timestamp)
stat	(String) -> Result[{size, is_dir, is_file, modified}, String]	Get file metadata

File Operations

Function	Signature	Description
copy	(String, String) -> Result[Unit, String]	Copy file
rename	(String, String) -> Result[Unit, String]	Rename or move file
remove	(String) -> Result[Unit, String]	Delete a file
remove_all	(String) -> Result[Unit, String]	Recursively delete directory

Temporary Files

Function	Signature	Description
temp_dir	() -> String	Get system temp directory
create_temp_file	(String) -> Result[String, String]	Create temp file with prefix
create_temp_dir	(String) -> Result[String, String]	Create temp directory with prefix

Examples

import fs

effect fn process_files() -> Result[Unit, String] = {
  let text = fs.read_text("input.txt")
  let lines = string.lines(text)
  let upper = list.map(lines, (l) => string.to_upper(l))
  fs.write("output.txt", string.join(upper, "\n"))
}

effect fn list_almd_files() -> Result[Unit, String] = {
  let files = fs.glob("src/**/*.almd")
  for f in files {
    println(f)
  }
  ok(())
}