85 Writing and reading a file

CreateNew claims a fresh filename and fails rather than overwriting an existing file. The writer is closed in finally before a bounded UTF-8 read returns the text.

import std.filesystem.FileWriteMode
import std.filesystem.Path
import std.filesystem.openWrite
import std.filesystem.readText
import std.io.TextEncoding
import std.io.encodeText

main() {
  Path note = Path(value: "note.txt")
  var writer = openWrite(path: note, mode: FileWriteMode.CreateNew)
  try {
    var content = encodeText(
      text: "Learn Norm",
      encoding: TextEncoding.Utf8
    )
    writer.write(content)
  } finally {
    writer.close()
  }
  String text = readText(
    path: note,
    encoding: TextEncoding.Utf8,
    maximumBytes: 1024
  )
  printLine(text)
}

From the Norm repository root, use a new, empty scratch directory:

mkdir .tmp/norm-file-lesson
cd .tmp/norm-file-lesson
norm run ../../norm/tests/docs/libraries/files/write_read.norm

Expected output:

Learn Norm

The program leaves its own note.txt in that scratch directory for the next lesson. Repeating the write without removing it fails while opening the existing file; the file is not overwritten.

Try it: Run the command twice and inspect the second failure.

Precise rules: Filesystem API.