Temporary Files And Directories in Nim

Throughout program execution, we often want to create data that isn’t needed after the program exits. Temporary files and directories are useful for this purpose since they don’t pollute the file system over time.

import os, strutils

proc check(e: ref Exception) =
  if not isNil(e):
    raise e

proc main() =
  # The easiest way to create a temporary file is by using
  # the `createTempFile` proc from the `os` module. It creates
  # a file and returns its name. We provide an empty string
  # as the first argument, so `createTempFile` will create
  # the file in the default location for our OS.
  let (f, err) = createTempFile("", "sample")
  check(err)

  # Display the name of the temporary file. On
  # Unix-based OSes the directory will likely be `/tmp`.
  # The file name starts with the prefix given as the
  # second argument to `createTempFile` and the rest
  # is chosen automatically to ensure that concurrent
  # calls will always create different file names.
  echo "Temp file name: ", f

  # Clean up the file after we're done. The OS is
  # likely to clean up temporary files by itself after
  # some time, but it's good practice to do this
  # explicitly.
  defer: removeFile(f)

  # We can write some data to the file.
  writeFile(f, @[1'u8, 2, 3, 4])

  # If we intend to create many temporary files, we may
  # prefer to create a temporary *directory*.
  # `createTempDir` works similarly to `createTempFile`,
  # but it returns a directory name rather than a file name.
  let (dname, dirErr) = createTempDir("", "sampledir")
  check(dirErr)
  echo "Temp dir name: ", dname

  defer: removeDir(dname)

  # Now we can synthesize temporary file names by
  # prefixing them with our temporary directory.
  let fname = dname / "file1"
  writeFile(fname, @[1'u8, 2])

main()

To run the program, save it as temp_files_and_dirs.nim and use the Nim compiler:

$ nim c -r temp_files_and_dirs.nim
Temp file name: /tmp/sample7052316073705954828
Temp dir name: /tmp/sampledir7052316073705954829

In this Nim version, we use the os module to handle file and directory operations. The createTempFile and createTempDir procs are used to create temporary files and directories, respectively. We use defer statements to ensure cleanup of resources, which is similar to Go’s defer.

Note that Nim’s error handling is different from Go’s. Instead of returning errors, Nim uses exceptions. The check proc is defined to raise an exception if an error occurs.

The writeFile proc is used to write data to files, and we use Nim’s sequence syntax @[] to create byte sequences.

The removeFile and removeDir procs are used for cleanup, similar to Go’s os.Remove and os.RemoveAll.

This Nim code provides equivalent functionality to the original example, demonstrating how to work with temporary files and directories in Nim.

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Temporary Files And Directories in Nim