Golang print to console

Golang print to console


  • Logging in Golang – How to Start
  • console.log for golang
  • go test -v streaming output
  • November 16, 2011
  • How to print a line to STDERR and STDOUT in Go?
  • Printing structure variables in console in Golang
  • Logging in Golang – How to Start

    When troubleshooting a bug in production, logging is often the difference between a quick fix and hours or days of fruitless investigation. This is true regardless of programming language or platform. Your app might be written in Java , Python, or a web framework , but logging remains equally important. A Brief Background on the Go Programming Language Go is an open-source programming language originally designed by Google in late The objective of Go is to be as efficient as a low-level language like C and cater to some of the same problems and challenges.

    However, it also offers developers some of the conveniences of more modern programming languages, such as memory safety, garbage collection, and support for parallel programming. What Is Logging? So what is logging? Logging is the act of keeping a log. In the simplest case, messages are written to a single log file. In a nutshell, we could say logging is writing information about your application to some external destination so you can go back later and read it. Even though the definition above emphasizes log files, there are plenty of destinations you can write your events to, including database tables, cloud services, and more.

    Why Bother? Logging is mainly used as a troubleshooting mechanism. This information can help you diagnose and fix whatever problem the application was presenting. But software organizations have been increasingly using logging in more proactive—rather than reactive—ways. By leveraging log analysis , organizations can extract valuable insights from their logs. They can then use this knowledge to help them in their decision-making processes and fix problems before they become critical.

    Paste the code below on a new text file and save it as golang-demo. Println "Hello, world! This is because the language offers a logging package you can use right off the bat. Start by importing the package. Add the following line to your code before the main function: import "log" Then, add the following line to your main function: log. Print "This is our first log message in Go. Logging to the console might be enough for performing simpler debugging tasks, but when it comes to logging in production or doing more robust debugging, this approach falls hopelessly short.

    Additionally, you might need to format your logging output in specific ways. Logging to a File There are many possible logging destinations, but the most popular is certainly files on disk. Our first task is to create a file to write to or open it, if it already exists.

    Add the following code to your main function above the calling to log. OpenFile "golang-demo. But if you go to the folder where your golang-demo. The next step is to set our file as the output for the logger. Add the following line right before the call to log. Print: log. SetOutput file Run the program again and open your log file. Working With Levels We used the function Fatalf to handle issues when opening or creating our log file. Even though the function shares the name of one of the common logging levels offered by most logging tools, it actually calls os.

    Exit 1 after writing the message, which terminates the program. So how do you use log levels with the standard logging package in Go? For a long time, logrus was the most popular logging framework for Go. To install zap, run go get -u go. Then, remove the os package from your list of imports and replace it with this: import "go. Info "This is our first log message using zap! Logging is essential for most nontrivial applications.

    Go offers a standard logging package you can use from the get-go. The package is somewhat limited, though, so we had to resort to a third-party tool—zap—to obtain features such as structured logging and levels. So what should your next steps be?

    Well, you have an exciting and long journey of learning ahead of you. Here are some things you might try next: — Learn more about the available logging tools. Give it a try today. Carlos is a.

    console.log for golang

    Logging is an act of keeping a log. In the simplest case, messages are written to a single log file. Golang Log The package log in Golang implements the simple logging package. It defines a type, Logger, with methods for formatting output. Golang Log will be helpful in the critical scenarios in real-time applications. Large corporations that depend on the distributed systems often write their applications in Go to take advantage of the concurrency features like channels and goroutines e.

    If you are responsible for building or supporting the Go applications, a well-considered logging strategy can help you to understand user behavior, localize errors, and monitor the performance of your applications. How to use log in Golang Golang has an inbuilt logging library , called log, comes with the default logger that writes to standard error and adds the timestamp without the need for configuration. You can use these rough-and-ready logs for local development in which you need to get fast feedback from your code may be more important than generating rich, structured logs.

    If you want to generate rich and structured logs then third party packages will be more helpful. For example, you can define the division function that returns the error to the caller rather than exiting the program when you attempt to divide by zero.

    See the following code. We are checking the dividing by 0 error, and if it occurs, then we log that error in console. If we met the divide by 0 condition, then one error will be generated, and then we log that error in the console and also prints the return value in the console.

    In the above program, we got the divide by 0 condition; that is why we got the output log. The logger writes to standard error and prints the date and time of each logged message which is quite useful in general case scenarios. Every log message has an output on the separate line: if the message being printed does not end in the new line, the logger will add one line. The Fatal functions call os.

    Exit 1 after writing the log message. The Panic functions call panic after writing a log message. How to store the logged messages in files in Go In the above code, we have print the log message in the console. OpenFile "info. Close log. SetOutput file log. Print exception fmt. Open the file, and you will see something like the following printed. Features not generally available appear in the system-specific package syscall. If the open fails on file, then the error string will be self-explanatory.

    What we are doing in the above code is that we are creating one log file and print our log message inside that file. After printing the log message, we are closing the file, and that is it. Github package logrus for formatted logs The logrus , a logging package designed for structured logging that is well-suited for logging in JSON.

    And since JSON is a well-defined standard, it makes it straightforward to add context by including new fields—a parser should be able to pick them up automatically. Using the logrus package, you can define standard fields to add to your JSON logs by using the function WithFields, as shown below.

    You can then make calls to the logger at different levels, such as Info , Warn , and Error. Now, to use the package, first, you need to install it.

    Type the following command. WithFields log. Writer, see below for File example log. SetOutput os. SetLevel log. Info "A group of walrus emerges from the ocean" log. Warn "The group's number increased tremendously! Fatal "The ice breaks! Info "I'll be logged with common and other field" contextLogger. You can make calls to the logger from within your primary application process, not within goroutines.

    It is considered good practice if you write logs from your application to a local file, even if you will ship them to a central platform later. You can standardize your logs with a set of predefined messages. You can send your logs to the central platform so you can analyze and aggregate them. Conclusion In this post, we have gone through the benefits and tradeoffs of several Go logging libraries.

    We have also recommended ways to ensure that your logs are available and accessible when you need them and the information they contain is handy, consistent and easy to analyze. Finally, the Golang Log article is over. Recommended Posts.

    go test -v streaming output

    Additionally, you might need to format your logging output in specific ways. Logging to a File There are many possible logging destinations, but the most popular is certainly files on disk.

    Our first task is to create a file to write to or open it, if it already exists. Add the following code to your main function above the calling to log.

    OpenFile "golang-demo. But if you go to the folder where your golang-demo. The next step is to set our file as the output for the logger. Add the following line right before the call to log. Print: log. SetOutput file Run the program again and open your log file. Working With Levels We used the function Fatalf to handle issues when opening or creating our log file.

    Even though the function shares the name of one of the common logging levels offered by most logging tools, it actually calls os. Exit 1 after writing the message, which terminates the program. So how do you use log levels with the standard logging package in Go?

    For a long time, logrus was the most popular logging framework for Go. To install zap, run go get -u go. Then, remove the os package from your list of imports and replace it with this: import "go. Info "This is our first log message using zap! Logging is essential for most nontrivial applications. Go offers a standard logging package you can use from the get-go.

    November 16, 2011

    The package is somewhat limited, though, so we had to resort to a third-party tool—zap—to obtain features such as structured logging and levels. So what should your next steps be? Well, you have an exciting and long journey of learning ahead of you. Here are some things you might try next: — Learn more about the available logging tools.

    Give it a try today. In a nutshell, you need application logs to go back in time and understand how the application behaves in the real world.

    What Should You Log? The data that companies are storing with applications are becoming more relevant each day. Want proof? We need to be careful about what we put on those log files. In distributed systems, a tracking flag to replicate the request across all the different points of the system.

    Log levels such as panic, fatal, debug, or informational logs to give more context. With the simple approach we saw before, we might have some spaghetti code that will be hard to maintain and extend. Enter the Logging Framework Logging is an already-solved problem, and there are logging frameworks that will help you log easily.

    How to print a line to STDERR and STDOUT in Go?

    A framework will let you do the same things we did at the beginning of this guide but with fewer lines of code and a standard way of logging.

    In the Go ecosystem, there are actually a lot of logging frameworks. You can see them listed on the Awesome Go page on GitHub. The two most popular logging frameworks are Glog and Logrus.

    Google is the author of Glog. It keeps the simple style from Go, but no one has updated the GitHub repository for two years now. On the other hand, Logrus has been constantly supported by the community.

    And why would you need levels in logs? Debug "Useful debugging information. Info "Something noteworthy happened! Warn "You should probably take a look at this. Error "Something failed but I'm not quitting. Exit 1 after logging log. Fatal "Bye. Panic "I'm bailing.

    This will also help you make better use of the storage or data transfer in your infrastructure. SetLevel log. WarnLevel log. WithFields log.

    Printing structure variables in console in Golang

    Info "A group of walrus emerges from the ocean" log. Warn "The group's number increased tremendously! Fatal "The ice breaks! WarnLevel This line sets the log level we talked about before. Remember when I said earlier that the order of lines is important? The reason is that the log level also sets the importance of the logged message. The first level, debug, is the least important. And the last level, panic, is the most important.

    Only the warning and fatal log messages were written. It will be time-consuming as the application keeps growing. Where Do You Go Now? Logging frameworks are there to help you add logs to the application with just a few lines of code. What I really like about these frameworks is that you can guarantee that important data such as timestamps, context, and log levels is logged.

    Log levels can become your best friend when problems arise and you need to troubleshoot. By using log levels, you avoid being ashamed in demos with funny log messages that you might accidentally leave in the code.

    Final Thoughts In this post, I only just scratched the surface of Logrus logging framework. You can find useful information and examples by just going to the home page of the project on GitHub. You can configure hooks, log messages according to the environment, use formatters, and a lot of other things as per the docs site.


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