Temporary Files And Directories in Racket

#lang racket

(require racket/file)
(require racket/path)

(define (check e)
  (when e
    (error e)))

(define (main)
  ; The easiest way to create a temporary file is by
  ; using `make-temporary-file`. It creates a file and
  ; returns its path. We provide #f as the first argument
  ; to use the default temporary directory for our OS.
  (define-values (temp-path temp-port) 
    (make-temporary-file "sample~a" #f #f))
  
  ; 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
  ; first argument to `make-temporary-file` and the rest
  ; is chosen automatically to ensure that concurrent
  ; calls will always create different file names.
  (printf "Temp file name: ~a\n" temp-path)
  
  ; 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.
  (current-custodian-shutdown-all (make-custodian))
  
  ; We can write some data to the file.
  (write-bytes #"\1\2\3\4" temp-port)
  (close-output-port temp-port)
  
  ; If we intend to create many temporary files, we may
  ; prefer to create a temporary *directory*.
  ; `make-temporary-directory` works similarly to
  ; `make-temporary-file`, but it returns a directory path.
  (define temp-dir (make-temporary-directory "sampledir"))
  (printf "Temp dir name: ~a\n" temp-dir)
  
  ; Now we can synthesize temporary file names by
  ; prefixing them with our temporary directory.
  (define fname (build-path temp-dir "file1"))
  (with-output-to-file fname
    (lambda () (write-bytes #"\1\2"))
    #:exists 'replace))

(main)

To run this program, save it to a file (e.g., temp-files-and-dirs.rkt) and execute it using the Racket interpreter:

$ racket temp-files-and-dirs.rkt
Temp file name: /tmp/sample208395824
Temp dir name: /tmp/sampledir208395825

This Racket program demonstrates how to work with temporary files and directories. Here’s a breakdown of the key points:

We use make-temporary-file to create a temporary file. This function returns both the file path and a port for writing to the file.
The program prints the name of the temporary file, which will include the prefix we specified (“sample” in this case).
We use Racket’s custodian system to ensure the temporary file is cleaned up when we’re done. This is similar to the defer statement in the original example.
We write some data to the temporary file using write-bytes.
To create a temporary directory, we use make-temporary-directory.
Finally, we demonstrate how to create a file within the temporary directory using build-path and with-output-to-file.

Note that Racket’s file system functions handle many details automatically, such as choosing unique file names and cleaning up resources. This makes working with temporary files and directories in Racket quite straightforward.

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Temporary Files And Directories in Racket