How do I check if a file or directory exists in EK9?

← File I/O · Ref: Q153

EK9 provides the FileSystemPath type for working with file system paths. It supports checking existence, distinguishing files from directories, and performing path operations.

FILESYSTEMPATH TYPE

Create a FileSystemPath from a string:

  path <- FileSystemPath("/home/user/data.txt")

FileSystemPath represents a location on the file system without opening or reading the file.

CHECKING EXISTENCE

Use exists() to check if the path points to something on disk:

  if path.exists()
    stdout.println("Path exists")

The exists() method returns a Boolean that is set to true or false.

FILE VS DIRECTORY

Distinguish between files and directories:

  if path.isFile()
    stdout.println("It is a file")
  else if path.isDirectory()
    stdout.println("It is a directory")

You can also check isReadable(), isWritable(), and isExecutable().

PATH OPERATIONS

FileSystemPath supports several path manipulation methods:

  abs <- path.absolutePath()
  name <- path.fileName()
  parent <- path.parent()
  joined <- path + "subdir"

Use startsWith() and endsWith() for prefix and suffix checks.

See Q42 for the Path type. See Q151 for reading files. See Q152 for writing files.

Example

#!ek9
defines module qa.fileio.path

  defines program

    FilePathExistsDemo()
      stdout <- Stdout()

      // === CREATING FILESYSTEMPATH ===

      path <- FileSystemPath("/tmp")
      stdout.println("Path: " + $path)

      // === CHECKING EXISTENCE ===

      stdout.println("Exists: " + $path.exists())

      // === FILE VS DIRECTORY ===

      stdout.println("Is file: " + $path.isFile())
      stdout.println("Is directory: " + $path.isDirectory())

      // === PATH PROPERTIES ===

      stdout.println("Is readable: " + $path.isReadable())
      stdout.println("Is writable: " + $path.isWritable())
      stdout.println("Is absolute: " + $path.isAbsolute())

      // === PATH OPERATIONS ===

      absolutePath <- path.absolutePath()
      stdout.println("Absolute: " + $absolutePath)

      // Path concatenation with + operator
      subPath <- path + "subdir"
      stdout.println("Sub path: " + $subPath)

Common mistakes

E50060 — FileSystemPath constructor expects a String argument. Passing an Integer triggers E50060 — constructor not resolved because no FileSystemPath(Integer) exists. File paths are always represented as strings in EK9. See ek9 -h E50060 for details.

Incorrect:

path <- FileSystemPath(42)

Correct:

path <- FileSystemPath("/tmp")

E50060 — FileSystemPath has no fileExists() method. Use exists() to check if the path points to something on disk. See ek9 -h E50060 for details.

Incorrect:

stdout.println("Exists: " + $path.fileExists())

Correct:

stdout.println("Exists: " + $path.exists())

E50060 — FileSystemPath has no getAbsolutePath() method. Use absolutePath() to get the absolute path. EK9 uses descriptive method names rather than Java-style getters. See ek9 -h E50060 for details.

Incorrect:

absolutePath <- path.getAbsolutePath()

Correct:

absolutePath <- path.absolutePath()

Coming from another language?

Java: Files.exists(Path) and Path for path operations. Python: os.path.exists() or pathlib.Path. Rust: Path::exists() and std::path::Path. Go: os.Stat() for existence checks. EK9: FileSystemPath('/path') with exists(), isFile(), isDirectory() methods and + operator for path joining.

Keywords: check, directory, exists, file, filesystem, folder, isDirectory, isFile, path, read, write