Fuzion • Idioms • Idiom # 95: Get file size

Idiom # 95: Get file size

Code

The variable x in this case will be of type outcome i64, i.e., it will be either the file size or an instance of error in case the file size could not be determined. A match expression is needed to extract the size.

Alternatively, the following code forcefully extracts the size from the result, but will crash in case of an error:

Running Example

ex95 is

  lm : mutate is

  lm.instate_self ()->

    path := "idiom95.testfile"

    # create the file
    o0 := io.file.use unit lm path io.file.mode.write ()->
      _ := (io.buffered.writer lm).write "hello".utf8
    handle_error o0

    # size without error handling, will set x to choice type `outcome i64`
    x0 := (io.file.stat path true).bind i64 x->x.size
    say "the size of $path is $x0"

    # size without error handling, will fail at precondition or panic in case of an error
    x1 := (io.file.stat path true).val.size
    say "the size of $path is $x1"

    # size with manual error handling
    match io.file.stat path true
      d io.file.meta_data => x := d.size                   # logic in case of success
                             say "the size of $path is $x"
      e error             => say e                         # error handling

    # delete the file
    o1 := io.file.delete path
    handle_error o1

    handle_error (e outcome T) =>
      if e!!
        panic $e.err

What are effects?

last changed: 2024-07-01

next: Idiom # 96: Check string prefix