OPEN-FILE-INPUT-PORT(3scm)

okay bestie, this is the open-file-input-port(3scm) page from the Scheme Programmer's Manual — and it's literally all about opening a file for reading. Group chat, gather round. 💖

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🎀 NAME 🎀

open-file-input-port — open a file for reading. That's the whole plot, and it ate. 💅

📚 LIBRARY 📚

(import (rnrs))                     ;R6RS
(import (rnrs io ports))            ;R6RS

✨ SYNOPSIS ✨

(open-file-input-port filename)
(open-file-input-port filename file-options)
(open-file-input-port filename file-options buffer-mode)
(open-file-input-port filename file-options buffer-mode maybe-transcoder)

🌸 DESCRIPTION 🌸

Returns an input port for the named file. Slay. 💖

• The file-options argument defaults to the value of (file-options). Heads up: the standard file options do nothing for input ports.
• The buffer-mode argument must be one of the symbols that name a buffer mode. It defaults to block. Also, note that line buffering is unlikely to be effective on input ports.

🦋 Textual ports 🦋

If maybe-transcoder is a transcoder, it becomes the transcoder associated with the returned port. The port will then be a textual port. Cute. ✨

🧚 Binary ports 🧚

If maybe-transcoder is #f or absent, the port will be a binary port.

👑 Port positioning 👑

The port will support the port-position(3scm) and set-port-position!(3scm) operations if it is a binary port. Otherwise support is implementation-dependent, and possibly transcoder-dependent. iykyk. 💫

🫶 RETURN VALUES 🫶

Returns a single value; a binary or textual input port. One value, no drama.

🌈 EXAMPLES 🌈

No cap, here's the example — it returns all records in /etc/passwd:

;; Return all records in /etc/passwd
(call-with-port
   (open-file-input-port "/etc/passwd"
                         (file-options)
                         (buffer-mode block)
                         (native-transcoder))
  (lambda (p)
    (let lp ()
      (let ((line (get-line p)))
         (if (eof-object? line)
             '()
             (cons line (lp)))))))

🍓 APPLICATION USAGE 🍓

This is used in applications that open binary files, and ones that open textual files while needing control over the transcoder. Very demure, very mindful. 💅

💀 COMPATIBILITY 💀

This procedure is unique to R6RS. Other RnRS revisions have open-input-file(3scm), which is also in R6RS. History lesson, bestie. 📚

🚨 ERRORS 🚨

This procedure can raise exceptions with the following condition types:

• &assertion (R6RS) — The wrong number of arguments was passed or an argument was outside its domain. In particular, maybe-transcoder must be either a transcoder or #f.
• R7RS — The assertions described above are errors. Implementations may signal an error, extend the procedure's domain of definition to include such arguments, or fail catastrophically. 💀😭

🎀 SEE ALSO 🎀

• file-options(7scm)
• buffer-mode(7scm)
• open-input-file(3scm)
• open-file-output-port(3scm)

⭐ STANDARDS ⭐

R6RS. That's it, that's the standard. ✨

🔥 HISTORY 🔥

First appeared in the reworked I/O system in R6RS. A glow-up moment, fr fr. 💖

💜 AUTHORS 💜

This page is part of the scheme-manpages project. It includes materials from the RnRS documents. More information can be found at https://github.com/schemedoc/manpages/.

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💖 okay that's the whole page — source/version tag: open-file-input-port(3scm), date: 2022-05-10. Byeeee! 👋💅