Reading Files Character-by-Character with InputStream

Welcome to this lesson on reading files character by character. Building upon our foundational knowledge of handling text files, this lesson will guide you through utilizing input streams to read files character by character. These methods are crucial for handling varying file sizes efficiently and managing memory use effectively. By the end of this lesson, you'll be able to read entire files, specific portions, and process files in manageable chunks, granting you flexible control over text data processing.

Before we jump into reading files, let's review the example file that we will work with:

Hi!
This file contains some sample example text to use to test how the read method works.
Let's do some programming!

This file contains multiple lines of varied lengths.

The InputStream is designed for reading data from a source in the form of bytes, and it can be used for reading files as a stream of characters. It provides methods to open a file and read its contents character by character, which is helpful for detailed text processing. To read a file's entire content character by character, we open the file using an input stream and utilize the read() method, which reads the next byte in the stream and returns its integer representation.

Here is how to read a file completely character by character using a loop:

import os._

@main def main() =
  // Specify the file path
  val filePath = os.pwd / "example.txt"

  println("Reading file character-by-character:")

  // Open the file and get an input stream
  val inputStream = os.read.inputStream(filePath)

  // Read the first byte from the input stream
  var byte = inputStream.read()
  
  // Continue reading until the end of the file is reached
  while (byte != -1) {
    // Convert the byte to a character and print it
    print(byte.toChar)
    // Read the next byte
    byte = inputStream.read()
  }

  // Close the input stream after processing
  inputStream.close()

The read() method reads a byte from the file and returns its integer representation, which is then cast back to a character using toChar. The loop continues until all characters have been read. It is crucial to close the input stream after the operations to release system resources and prevent potential file locks.

The expected output is:

Hi!
This file contains some sample example text to use to test how the read method works.
Let's do some programming!

This approach suits situations where processing files one character at a time is necessary or preferred. It provides a straightforward way to read entire files while maintaining resource efficiency, making input streams a versatile option for file manipulation.