Temporary Files And Directories in Standard ML

In Standard ML, we can create temporary files and directories using the OS.FileSys structure. However, Standard ML doesn’t have built-in functions for creating temporary files or directories, so we’ll simulate this behavior using the current time to generate unique names.

structure TempFiles = struct
  (* Helper function to generate a unique name *)
  fun generateUniqueName prefix =
    let
      val time = Time.toMilliseconds(Time.now())
    in
      prefix ^ Int.toString(time)
    end

  (* Function to create a temporary file *)
  fun createTempFile prefix =
    let
      val fileName = generateUniqueName prefix
      val outStream = TextIO.openOut fileName
    in
      (fileName, outStream)
    end

  (* Function to write to a file *)
  fun writeToFile (outStream, data) =
    TextIO.output(outStream, data)

  (* Function to close and delete a file *)
  fun closeAndDeleteFile (fileName, outStream) =
    (TextIO.closeOut outStream;
     OS.FileSys.remove fileName)

  (* Function to create a temporary directory *)
  fun createTempDir prefix =
    let
      val dirName = generateUniqueName prefix
    in
      (OS.FileSys.mkDir dirName; dirName)
    end

  (* Function to remove a directory *)
  val removeDir = OS.FileSys.rmDir

  (* Main function *)
  fun main () =
    let
      val (tempFileName, tempFileStream) = createTempFile "sample"
      val _ = print ("Temp file name: " ^ tempFileName ^ "\n")
      val _ = writeToFile (tempFileStream, "1234")
      val _ = closeAndDeleteFile (tempFileName, tempFileStream)

      val tempDirName = createTempDir "sampledir"
      val _ = print ("Temp dir name: " ^ tempDirName ^ "\n")
      val _ = removeDir tempDirName
    in
      ()
    end
end

(* Run the main function *)
val _ = TempFiles.main()

This Standard ML code demonstrates the creation and usage of temporary files and directories:

We define a TempFiles structure to encapsulate our functions.
generateUniqueName creates a unique name by appending the current time in milliseconds to a given prefix.
createTempFile simulates creating a temporary file by generating a unique name and opening a file with that name.
writeToFile writes data to the file.
closeAndDeleteFile closes the file stream and removes the file.
createTempDir creates a temporary directory with a unique name.
removeDir removes a directory.
In the main function, we demonstrate the usage of these functions:
- Create a temporary file, write to it, and then delete it.
- Create a temporary directory and then remove it.

To run this program, save it to a file (e.g., temp_files.sml) and use your Standard ML interpreter. For example, with SML/NJ:

$ sml temp_files.sml
Temp file name: sample1234567890
Temp dir name: sampledir1234567891

Note that the actual file and directory names will vary based on the current time when you run the program.

This implementation provides similar functionality to the original example, allowing for the creation and management of temporary files and directories in Standard ML.

Command Line Subcommands in Standard ML

Logging in Standard ML

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Temporary Files And Directories in Standard ML