Book Image

Go Systems Programming

Book Image

Go Systems Programming

Overview of this book

Go is the new systems programming language for Linux and Unix systems. It is also the language in which some of the most prominent cloud-level systems have been written, such as Docker. Where C programmers used to rule, Go programmers are in demand to write highly optimized systems programming code. Created by some of the original designers of C and Unix, Go expands the systems programmers toolkit and adds a mature, clear programming language. Traditional system applications become easier to write since pointers are not relevant and garbage collection has taken away the most problematic area for low-level systems code: memory management. This book opens up the world of high-performance Unix system applications to the beginning Go programmer. It does not get stuck on single systems or even system types, but tries to expand the original teachings from Unix system level programming to all types of servers, the cloud, and the web.

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Table of Contents (13 chapters)
Preface
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Free Chapter
1
Getting Started with Go and Unix Systems Programming
Getting Started with Go and Unix Systems Programming
The structure of the book
What is systems programming?
About Go
Two useful Go tools
The various states of a Unix process
Exercises
Summary
2
Writing Programs in Go
Writing Programs in Go
Compiling Go code
Go environment variables
Using command-line arguments
User input and output
Go functions
Go data structures
Interfaces
Creating random numbers
Exercises
Summary
3
Advanced Go Features
Advanced Go Features
Error handling in Go
Pattern matching and regular expressions
Reflection
Comparing Go to other programming languages
Analysing software
Unreachable code
Avoiding common Go mistakes
Exercises
Summary
4
Go Packages, Algorithms, and Data Structures
Go Packages, Algorithms, and Data Structures
About algorithms
Sorting algorithms
Linked lists in Go
Trees in Go
Developing a hash table in Go
About Go packages
Garbage collection
Your environment
Go gets updated frequently!
Exercises
Summary
5
Files and Directories
Files and Directories
Useful Go packages
Command-line arguments revisited!
Dealing with directories
Dealing with files in Go
Developing find(1) in Go
The first version of find(1)
Using regular expressions
Exercises
Summary
6
File Input and Output
File Input and Output
About file input and output
Useful I/O packages in Go
File I/O operations
Copying files in Go
Developing wc(1) in Go
Interprocess communication
Sparse files in Go
Reading and writing data records
File locking in Go
A simplified Go version of the dd utility
Exercises
Summary
7
Working with System Files
Working with System Files
Which files are considered system files?
Logging in Go
Putting data at the end of a file
About log files
More pattern matching examples
Searching files revisited
Date and time operations
Rotating log files
Creating good random passwords
Another Go update
Exercises
Summary
8
Processes and Signals
Processes and Signals
About Unix processes and signals
Process management
Unix signals in Go
The kill(1) command
Improving file copying
Plotting data
Unix pipes in Go
Unix sockets in Go
RPC in Go
Programming a Unix shell in Go
Yet another minor Go update
Exercises
Summary
9
Goroutines - Basic Features
Goroutines - Basic Features
About goroutines
The sync Go packages
Pipelines
A better version of wc.go
Exercises
Summary
10
Goroutines - Advanced Features
Goroutines - Advanced Features
The Go scheduler
The sync Go package
The select keyword
Signal channels
Buffered channels
About timeouts
Channels of channels
Nil channels
Shared memory
The dWC.go utility revisited
Detecting race conditions
About GOMAXPROCS
Exercises
Summary
11
Writing Web Applications in Go
Writing Web Applications in Go
What is a web application?
About the net/http Go package
Developing web clients
A small web server
The html/template package
About JSON
Using MongoDB
A handy command-line utility
Exercises
Summary
12
Network Programming
Network Programming
About network programming
The net Go standard package
Unix sockets revisited
Performing DNS lookups
Developing a simple TCP server
Developing a simple TCP client
Developing a simple UDP server
Developing a simple UDP client
A concurrent TCP server
Remote procedure call (RPC)
Exercises
Summary

Improving file copying

The original cp(1) utility prints useful information when it receives a SIGINFO signal, as shown in the following output:

$ cp FileToCopy /tmp/copy
FileToCopy -> /tmp/copy  26%
FileToCopy -> /tmp/copy  29%
FileToCopy -> /tmp/copy  31%

So, the rest of this section will implement the same functionality to the Go implementation of the cp(1) command. The Go code in this section will be based on the cp.go program because it can be very slow when used with a small buffer size giving us time for testing. The name of the new copy utility will be cpSignal.go and will be presented in four parts.

The fundamental difference between cpSignal.go and cp.go is that cpSignal.go should find the size of the input file and keep the number of bytes that have been written at a given point. Apart from those modifications there is nothing else that you should worry about...

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