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Input

Reads a line of text from standard input.

Module: Std::Io

Summary

import Std::Io::{ ReadLine, PrintLine };
import Std::Display;

func Main() -> int {
    PrintLine("Enter your name:");

    let name = ReadLine();

    PrintLine("Hello, {}!", name);

    return 0;
}

Description

ReadLine reads a line of UTF-8 text from standard input and returns it as a String.

Trailing line terminators are automatically removed before the result is returned.

If an error occurs or end-of-file (EOF) is reached, an empty string is returned.

Line Terminators

ReadLine() automatically removes trailing line terminators.

The following sequences are recognized:

\n
\r\n

Example:

Input:

Hello World\n

Returned string:

Hello World

Empty Input

If the user presses Enter without typing any characters:

Input:

Returned value:

String::New()

Example

let text = ReadLine();

if text.IsEmpty() {
    PrintLine("No input");
}

Memory Management

The returned string owns its character buffer.

Memory is dynamically allocated before the string is returned.

Example

let text = ReadLine();

The returned string remains valid after the function returns.

Notes

  • Input is read as UTF-8 text.
  • Line terminators are removed automatically.
  • A new string is allocated for every successful call.
  • An empty string may indicate EOF, an input error, or an empty line.

Platform Notes

Linux / BSD / Illumos

  • Input is read from standard input using the read syscall (4096-byte buffer).
  • Linux: SYS_READ = 0 (negative errno).
  • BSD / Illumos: SYS_READ = 3 (positive errno).
  • Trailing \n and \r are stripped from the returned string.

Windows

  • Input is read from the standard input handle using the Windows file API.
  • UTF-8 input is returned directly.