Go Systems Programming: Master Linux and Unix system level programming with Go

 Cover....1 Title Page....2 Copyright....3 Credits....4 About the Author....5 About the Reviewer....6 www.PacktPub.com....7 Customer Feedback....8 Table of Contents....9 Preface....17 Chapter 1: Getting Started with Go and Unix Systems Programming....25 The structure of the book....26 What is systems programming?....26 Learning systems programming....28 About Go....29 Getting ready for Go....30 Two useful Go tools....31 Advantages and disadvantages of Go....35 The various states of a Unix process....36 Exercises....38 Summary....38 Chapter 2: Writing Programs in Go....39 Compiling Go code....39 Checking the size of the executable file....42 Go environment variables....43 Using command-line arguments....45 Finding the sum of the command-line arguments....46 User input and output....49 Getting user input....49 Printing output....51 Go functions....51 Naming the return values of a Go function....52 Anonymous functions....52 Illustrating Go functions....52 The defer keyword....55 Using pointer variables in functions....58 Go data structures....59 Arrays....59 Slices....61 Maps....64 Converting an array into a map....66 Structures....67 Interfaces....69 Creating random numbers....72 Exercises....74 Summary....75 Chapter 3: Advanced Go Features....76 Error handling in Go....76 Functions can return error variables....77 About error logging....79 The addCLA.go program revisited....81 Pattern matching and regular expressions....82 Printing all the values from a given column of a line....84 Creating summaries....85 Finding the number of occurrences....87 Find and replace....89 Reflection....90 Calling C code from Go....92 Unsafe code....93 Comparing Go to other programming languages....94 Analysing software....96 Using the strace(1) command-line utility....96 The DTrace utility....99 Disabling System Integrity Protection on macOS....102 Unreachable code....102 Avoiding common Go mistakes....104 Exercises....104 Summary....105 Chapter 4: Go Packages, Algorithms, and Data Structures....106 About algorithms....107 The Big O notation....107 Sorting algorithms....108 The sort.Slice() function....108 Linked lists in Go....110 Trees in Go....114 Developing a hash table in Go....116 About Go packages....120 Using standard Go packages....120 Creating your own packages....121 Private variables and functions....123 The init() function....123 Using your own Go packages....124 Using external Go packages....125 The go clean command....128 Garbage collection....128 Your environment....130 Go gets updated frequently!....132 Exercises....132 Summary....133 Chapter 5: Files and Directories....134 Useful Go packages....135 Command-line arguments revisited!....135 The flag package....135 Dealing with directories....138 About symbolic links....139 Implementing the pwd(1) command....140 Developing the which(1) utility in Go....142 Printing the permission bits of a file or directory....145 Dealing with files in Go....146 Deleting a file....146 Renaming and moving files....148 Developing find(1) in Go....150 Traversing a directory tree....151 Visiting directories only!....152 The first version of find(1)....153 Adding some command-line options....155 Excluding filenames from the find output....158 Excluding a file extension from the find output....160 Using regular expressions....161 Creating a copy of a directory structure....162 Exercises....167 Summary....167 Chapter 6: File Input and Output....168 About file input and output....169 Byte slices....169 About binary files....171 Useful I/O packages in Go....172 The io package....173 The bufio package....174 File I/O operations....176 Writing to files using fmt.Fprintf()....176 About io.Writer and io.Reader....177 Finding out the third column of a line....179 Copying files in Go....182 There is more than one way to copy a file!....182 Copying text files....182 Using io.Copy....182 Reading a file all at once!....184 An even better file copy program....186 Benchmarking file copying operations....189 Developing wc(1) in Go....194 Counting words....194 The wc.go code!....194 Comparing the performance of wc.go and wc(1)....199 Reading a text file character by character....200 Doing some file editing!....202 Interprocess communication....204 Sparse files in Go....204 Reading and writing data records....207 File locking in Go....210 A simplified Go version of the dd utility....213 Exercises....216 Summary....216 Chapter 7: Working with System Files....217 Which files are considered system files?....218 Logging in Go....218 Putting data at the end of a file....218 Altering existing data....220 About log files....222 About logging....223 Logging facilities....223 Logging levels....223 The syslog Go package....224 Processing log files....226 File permissions revisited....230 Changing file permissions....232 Finding other kinds of information about files....234 More pattern matching examples....237 A simple pattern matching example....237 An advanced example of pattern matching....240 Renaming multiple files using regular expressions....243 Searching files revisited....245 Finding the user ID of a user....245 Finding all the groups a user belongs to....247 Finding files that belong or do not belong to a given user....249 Finding files based on their permissions....252 Date and time operations....254 Playing with dates and times....254 Reformatting the times in a log file....256 Rotating log files....258 Creating good random passwords....261 Another Go update....263 Exercises....263 Summary....264 Chapter 8: Processes and Signals....265 About Unix processes and signals....266 Process management....266 About Unix signals....267 Unix signals in Go....268 The kill(1) command....268 A simple signal handler in Go....269 Handling three different signals!....271 Catching every signal that can be handled....273 Rotating log files revisited!....275 Improving file copying....278 Plotting data....282 Unix pipes in Go....289 Reading from standard input....290 Sending data to standard output....292 Implementing cat(1) in Go....293 The plotIP.go utility revisited....294 Unix sockets in Go....302 RPC in Go....303 Programming a Unix shell in Go....304 Yet another minor Go update....306 Exercises....306 Summary....307 Chapter 9: Goroutines — Basic Features....308 About goroutines....309 Concurrency and parallelism....309 The sync Go packages....310 A simple example....310 Creating multiple goroutines....311 Waiting for goroutines to finish their jobs....313 Creating a dynamic number of goroutines....315 About channels....317 Writing to a channel....317 Reading from a channel....319 Explaining h1s.go....320 Pipelines....321 A better version of wc.go....323 Calculating totals....326 Doing some benchmarking....330 Exercises....332 Summary....332 Chapter 10: Goroutines — Advanced Features....333 The Go scheduler....334 The sync Go package....334 The select keyword....334 Signal channels....337 Buffered channels....340 About timeouts....342 An alternative way to implement timeouts....344 Channels of channels....346 Nil channels....348 Shared memory....349 Using sync.Mutex....351 Using sync.RWMutex....355 The dWC.go utility revisited....358 Using a buffered channel....358 Using shared memory....361 More benchmarking....364 Detecting race conditions....365 About GOMAXPROCS....368 Exercises....370 Summary....370 Chapter 11: Writing Web Applications in Go....371 What is a web application?....372 About the net/http Go package....372 Developing web clients....372 Fetching a single URL....372 Setting a timeout....374 Developing better web clients....376 A small web server....379 The http.ServeMux type....382 Using http.ServeMux....382 The html/template package....386 About JSON....391 Saving JSON data....392 Parsing JSON data....394 Using Marshal() and Unmarshal()....396 Using MongoDB....398 Basic MongoDB administration....398 Using the MongoDB Go driver....401 Creating a Go application that displays MongoDB data....404 Creating an application that displays MySQL data....408 A handy command-line utility....411 Exercises....415 Summary....416 Chapter 12: Network Programming....417 About network programming....418 About TCP/IP....418 About TCP....418 The TCP handshake!....419 About UDP and IP....419 About Wireshark and tshark....420 About the netcat utility....422 The net Go standard package....422 Unix sockets revisited....423 A Unix socket server....423 A Unix socket client....425 Performing DNS lookups....427 Using an IP address as input....428 Using a host name as input....429 Getting NS records for a domain....431 Developing a simple TCP server....432 Developing a simple TCP client....435 Using other functions for the TCP server....437 Using alternative functions for the TCP client....439 Developing a simple UDP server....440 Developing a simple UDP client....442 A concurrent TCP server....444 Remote procedure call (RPC)....446 An RPC server....447 An RPC client....450 Exercises....452 Summary....453 Index....454