Or the scanner loop might've terminated due to an // error prematurely. Println ( 'word list:' ) // we are iterating only until the value of 'pos' because our buffer size // might be more than the number of words because we increase the length by // a constant value. Open ( 'filetoread.txt' ) if err != nil fmt. Having a handle to the os.File object, we can query the size and instantiate a list of bytes upfront.

We need to know the size of the file upfront in order to instantiate a buffer large enough to hold it.

We’ll start with a basic case that’s provided in the os package. To start off, the standard library provides multiple functions and utilities to read file data. Reading byte-wise Reading the entire file into memory This should not be taken as a general advice when shipping production code, though. To have a simpler mental model for this post, I’m converting an array of bytes to a string using the case string(arrayOfBytes). There is a benefit of not auto-converting everything to a string, one of which is to avoid expensive string allocations which increases GC pressure. In Go-and for that matter, most low level languages and some dynamic languages like Node-return a bytestream.

I’m uploading all the working examples to kgrz/reading-files-in-go.

These blog posts are are two really good resources to understand the differences.

I’ll be using the words “array” and “slice” interchangeably to refer to slices most of the time, but they are NOT the same.

All code examples are wrapped inside a main() function block.

The methods are not necessarily in decreasing order of simplicity. That was the main impulse that made me write the techniques down. When I started learning Go, it was hard for me to find out the easist way to do this. In fact, we run a good load of unit tests against DOMPurify before each new. In this year’s Advent of Code 2017 there were many problems that required different styles of reading input, and I ended up using most of them. This two-day training will be given by Dr.-Ing. This post is intended to serve as a quick intro to many options in the Go standard library to read files.

How to scan a file before ing