Temporary Files And Directories in Scheme

Our program demonstrates how to work with temporary files and directories. Here’s the full source code:

(import (scheme base)
        (scheme file)
        (scheme write))

(define (check e)
  (when e
    (error "An error occurred" e)))

(define (main)
  ; Create a temporary file
  (let-values (((port filename) (open-temporary-file "sample")))
    (display "Temp file name: ")
    (display filename)
    (newline)
    
    ; Write some data to the file
    (write-bytevector #u8(1 2 3 4) port)
    (close-output-port port)
    
    ; Clean up the file after we're done
    (delete-file filename))
  
  ; Create a temporary directory
  (let ((temp-dir (create-temporary-directory "sampledir")))
    (display "Temp dir name: ")
    (display temp-dir)
    (newline)
    
    ; Create a file in the temporary directory
    (let ((file-path (string-append temp-dir "/file1")))
      (call-with-output-file file-path
        (lambda (port)
          (write-bytevector #u8(1 2) port))))
    
    ; Clean up the directory and its contents
    (delete-directory temp-dir #t)))

(main)

This Scheme program demonstrates the creation and usage of temporary files and directories. Let’s break it down:

1. We import necessary modules for file operations and writing.

2. The check function is defined to handle errors, similar to the original example.

3. In the main function:

   • We create a temporary file using open-temporary-file. This function returns a port and a filename.

   • We display the name of the temporary file.

   • We write some data to the file using write-bytevector.

   • After we’re done, we close the port and delete the file with delete-file.

   • Next, we create a temporary directory using create-temporary-directory.

   • We display the name of the temporary directory.

   • We create a file inside this directory using call-with-output-file and write some data to it.

   • Finally, we clean up by deleting the directory and its contents with delete-directory.

Note that Scheme doesn’t have a built-in way to defer actions, so we need to manually ensure that cleanup happens after we’re done using the temporary files and directories.

To run this program, save it as temp-files-and-dirs.scm and use your Scheme interpreter. For example:

$ scheme temp-files-and-dirs.scm
Temp file name: /tmp/sampleXXXXXX
Temp dir name: /tmp/sampledirXXXXXX

The exact names of the temporary files and directories will vary, but they will typically be in the system’s default temporary location (often /tmp on Unix-like systems) and include random characters to ensure uniqueness.