s c h e m a t i c s : c o o k b o o k

This Web

Other Webs

Schematics

RSS

Scheme Links

Reading An Entire Text File

Problem

You want to read the lines from a file and store them in a list, the way Python's File.readlines() does.

Solution

(define (readlines filename)
  (call-with-input-file filename
    (lambda (p)
      (let loop ((line (read-line p))
                 (result '()))
        (if (eof-object? line)
            (reverse result)
            (loop (read-line p) (cons line result)))))))

Discussion

Of course, if you want to read everything into a big string and process the string (like calling File.read() in Python), you can define the following:

(define (read-all path)
    (let ((size (file-size path)))
      (call-with-input-file path
        (lambda (p)
          (read-string size p)))))

MzScheme's call-with-input-file accepts a third argument which allows you to specify 'text or 'binary, 'text is used to handle platform differences in newlines.

Don't be fooled by read. read is for reading S-Expressions from a port (i.e. Scheme code). readline and read-string are for reading raw text.

Comments about this recipe

Contributors

-- GordonWeakliem - 13 Aug 2004