How to view Golang logs on Debian

This article introduces several methods to view Go language application logs on Debian systems:

Method 1: Use journalctl command

If your Go application runs as a systemd service, you can use the journalctl command to view its logs. Assuming your service is named my-go-app , use the following command:

 sudo journalctl -u my-go-app

The journalctl command also supports multiple options, such as viewing the logs of the last startup:

 sudo journalctl -b

Or view logs for a specific time period:

 sudo journalctl --since "2024-01-01" --until "2024-01-31"

For more information, please refer to freedesktop.org .

Method 2: Check the log files in the /var/log directory

Go applications usually write logs to files in the /var/log directory. You can use cat , less , grep and other commands to view these files. For example, view the syslog file:

 cat /var/log/syslog

Use the tail command to view the tail content of the log file in real time:

 tail -f /var/log/syslog

Use the grep command to filter the log content, for example, to find lines containing the "error" keyword:

 grep "error" /var/log/syslog

Method 3: Use a text editor

You can open and view log files using any text editor (such as nano , vim , emacs ). For example, use the nano editor to view the syslog file:

 sudo nano /var/log/syslog

Method 4: Use the built-in logging function of Go language

In your Go program, you can use log packages or third-party log libraries (such as logrus , zap ) to record and write logs to files. The following example uses log package to write a log to app.log file:

 package main

import (
    "log"
    "os"
)

func main() {
    logFile, err := os.OpenFile("app.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
    if err != nil {
        log.Fatal(err)
    }
    defer logFile.Close()
    log.SetOutput(logFile)

    log.Println("This is a log information.")
}

Then, use the above command to view the app.log file.

Note: root permissions may be required to view sensitive log files. Please use these commands with caution and be aware of potential privacy risks.

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