Scanf.Scanning(3)

💖 NAME 💖

okay so this is Scanf.Scanning(3) from the OCaml library manual — and the NAME section is literally just “no description” 😭 iconic minimalism, honestly. The way that this page is all about formatted input channels and scanning buffers but the NAME gave us nothing? not me side-eyeing the docs. Anyway, bestie, the Documentation section is where the actual main character energy lives, so let's go. 🫶

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🦋 Module 🦋

Scanf.Scanning — that's the module, periodt. 💅

📖 Documentation 📖

Module Scanning : sig end

• type in_channel — the notion of input channel for the Scanf module: those channels provide all the machinery necessary to read from any source of characters, including a in_channel value. A Scanf.Scanning.in_channel value is also called a formatted input channel or equivalently a scanning buffer. The type Scanf.Scanning.scanbuf below is an alias for Scanning.in_channel.

⚠️ note: a Scanning.in_channel is not concurrency-safe — concurrent use may produce arbitrary values or exceptions. 💀 it's giving chaos, fr fr.

Since 3.12. ✨

• type scanbuf = in_channel — the type of scanning buffers. A scanning buffer is the source from which a formatted input function gets characters. The scanning buffer holds the current state of the scan, plus a function to get the next char from the input, and a token buffer to store the string matched so far.

note: a scanning action may often require to examine one character in advance; when this 'lookahead' character does not belong to the token read, it is stored back in the scanning buffer and becomes the next character yet to be read. 🦋 lowkey the buffer is holding onto that extra char for later.

• val stdin : in_channel — the standard input notion for the Scanf module. Scanning.stdin is the Scanf.Scanning.in_channel formatted input channel attached to stdin.

note: in the interactive system, when input is read from stdin, the newline character that triggers evaluation is part of the input; thus, the scanning specifications must properly skip this additional newline character (for instance, simply add a '\n' as the last character of the format string). 😭 yes bestie, that newline is part of the input, don't ignore it.

Since 3.12. 💜

• type file_name = string — a convenient alias to designate a file name. Since 4.00. 🎀
• val open_in : file_name -> in_channel — Scanning.open_in fname returns a Scanf.Scanning.in_channel formatted input channel for bufferized reading in text mode from file fname.

note: open_in returns a formatted input channel that efficiently reads characters in large chunks; in contrast, from_channel below returns formatted input channels that must read one character at a time, leading to a much slower scanning rate. 🐌 vs 🚀, iykyk.

Since 3.12. 🌸

• val open_in_bin : file_name -> in_channel — Scanning.open_in_bin fname returns a Scanf.Scanning.in_channel formatted input channel for bufferized reading in binary mode from file fname. Since 3.12. 🔥
• val close_in : in_channel -> unit — closes the in_channel associated with the given Scanf.Scanning.in_channel formatted input channel. Since 3.12. 💅 periodt.
• val from_file : file_name -> in_channel — an alias for Scanf.Scanning.open_in above. 🫶
• val from_file_bin : string -> in_channel — an alias for Scanf.Scanning.open_in_bin above. 👀
• val from_string : string -> in_channel — Scanning.from_string s returns a Scanf.Scanning.in_channel formatted input channel which reads from the given string. Reading starts from the first character in the string. The end-of-input condition is set when the end of the string is reached. 🍓 ate.
• val from_function : (unit -> char) -> in_channel — Scanning.from_function f returns a Scanf.Scanning.in_channel formatted input channel with the given function as its reading method. When scanning needs one more character, the given function is called. When the function has no more character to provide, it must signal an end-of-input condition by raising the exception End_of_file. 🔥 no cap.
• val from_channel : in_channel -> in_channel — Scanning.from_channel ic returns a Scanf.Scanning.in_channel formatted input channel which reads from the regular in_channel input channel ic argument. Reading starts at current reading position of ic. 👑
• val end_of_input : in_channel -> bool — Scanning.end_of_input ic tests the end-of-input condition of the given Scanf.Scanning.in_channel formatted input channel. ✅ vibe check: are we at the end?
• val beginning_of_input : in_channel -> bool — Scanning.beginning_of_input ic tests the beginning of input condition of the given Scanf.Scanning.in_channel formatted input channel. 🌅
• val name_of_input : in_channel -> string — Scanning.name_of_input ic returns the name of the character source for the given Scanf.Scanning.in_channel formatted input channel. Since 3.09. 🌈

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mwah 💋 this page was brought to you by OCamldoc, dated 2026-06-22, for Scanf.Scanning(3) — go forth and scan your little heart out, bestie 🫶✨