File open flags that determine how a file is opened and what operations are allowed.

Details

These flags correspond to standard POSIX file open modes and control the file access permissions and behavior when opening files.

• "r" - Read-only. File must exist.
• "r+" - Read/write. File must exist.
• "w" - Write-only. Truncates file to zero length or creates new file.
• "wx" - Like 'w' but fails if file exists.
• "w+" - Read/write. Truncates file to zero length or creates new file.
• "wx+" - Like 'w+' but fails if file exists.
• "a" - Write-only. Appends to file or creates new file.
• "ax" - Like 'a' but fails if file exists.
• "a+" - Read/write. Appends to file or creates new file.
• "ax+" - Like 'a+' but fails if file exists.

Example (Opening files with flags)

import { Effect, FileSystem } from "effect"

const program = Effect.gen(function*() {
  const fs = yield* FileSystem.FileSystem

  // Open for reading only
  const readFile = yield* fs.open("data.txt", { flag: "r" })

  // Open for writing, truncating existing content
  const writeFile = yield* fs.open("output.txt", { flag: "w" })

  // Open for appending
  const appendFile = yield* fs.open("log.txt", { flag: "a" })

  // Open for read/write, but fail if file doesn't exist
  const editFile = yield* fs.open("config.json", { flag: "r+" })
})