Job Ready Go

Lesson 20File I/O and OS Operations

Up to this point, we've been working with data within our programs that we either created in our code or have had users enter. It is also important to be able to save and retrieve data. In this lesson, we will cover file functionality provided in Go that will let us input data into and output it from our programs. We will also add coverage of working with directories. For an added bonus, we will cover the use of command-line arguments with our Go programs.

LEARNING OBJECTIVES

By the end of this lesson, you will be able to:

• Read data from a file into memory.
• Seek data from specific areas within a file.
• Use a buffered reader when working with files.
• Apply the Go defer statement.
• Work with directories in a computer system.
• Access and use command-line arguments.

READING A FILE

You can perform standard input and output (I/O) operations on a file using the io/ioutil package in Go. This package provides routines to perform standard I/O operations such as reading and writing to files. The example in Listing 20.1 reads a file called flatland01.txt into memory and displays its contents as a string.

NOTE Code examples in this lesson use a file called flatland01.txt. This sample file is an extract from Edwin A. Abbott's novel Flatland, as downloaded from Project Gutenberg (www.gutenberg.org). It is distributed in the public domain. You can download a copy from:

https://the-software-guild.s3.amazonaws.com/golang/v1-2006/data-files/flatland01.txt ...