10 Bash Script Logging Best Practices
When writing bash scripts, it's important to include logging so you can easily debug your code. Here are 10 best practices for logging in bash scripts.
Logging is an essential part of any Bash script. It helps you track the progress of your script, debug errors, and monitor the performance of your system. But logging can be tricky, and it’s easy to make mistakes.
In this article, we’ll discuss 10 best practices for logging in Bash scripts. We’ll cover topics such as logging levels, log rotation, and log file naming conventions. By following these best practices, you can ensure that your Bash scripts are logging correctly and efficiently.
1. Log to syslog
Syslog is a centralized logging system that allows you to store and manage log data from multiple sources in one place. This makes it easier to search, analyze, and monitor your logs for any issues or anomalies.
Additionally, syslog can be configured to send alerts when certain conditions are met, such as when an error occurs or when a script runs longer than expected. This helps ensure that any potential problems with your scripts are caught quickly and addressed before they become major issues.
2. Use a dedicated log file
When you use a dedicated log file, it’s easier to track the progress of your script. You can quickly see what commands were executed and when they were executed. This makes debugging much simpler since you don’t have to search through other logs or output from other programs.
Additionally, using a dedicated log file allows you to easily monitor the performance of your script over time. By tracking how long each command takes to execute, you can identify any bottlenecks in your code and optimize accordingly.
3. Include the script name in each message
When you’re troubleshooting a problem, it’s often helpful to know which script is responsible for the log message. This can be especially useful if your system has multiple scripts running at once and they all write to the same log file. By including the script name in each message, you’ll be able to quickly identify which script is responsible for any given message.
Additionally, by including the script name in each message, you’ll also be able to easily search through logs for specific messages from a particular script. This will save you time when trying to debug an issue or track down a bug.
4. Use descriptive messages
When you’re troubleshooting a script, it’s important to have as much information as possible. If your log messages are too vague or generic, it can be difficult to determine what went wrong and why.
Descriptive messages should include the time of the event, the type of event (e.g., error, warning, etc.), and any relevant details about the event. This will help you quickly identify issues in your scripts and make debugging easier. Additionally, descriptive messages can also provide valuable insight into how users interact with your scripts, which can help you improve them over time.
5. Don’t use echo for logging
When you use echo for logging, the output is sent to stdout. This means that it will be visible in the terminal window and can easily get lost among other messages. It also makes it difficult to parse logs since they are not structured.
Instead of using echo, use a logging library such as logger or syslog-ng. These libraries allow you to log messages with different levels (e.g., info, warning, error) and provide more control over how your logs are formatted and where they are stored.
6. Avoid using shell built-ins and commands with non-standard options
Shell built-ins and commands with non-standard options are not portable across different versions of the shell, which can lead to unexpected results. For example, if you use a command that is only available in Bash 4.2 but your script runs on Bash 3.2, it will fail. Additionally, these types of commands may be deprecated or removed from future versions of the shell, so using them could cause compatibility issues down the line.
To ensure portability and maintainability, stick to standard POSIX compliant commands and avoid using shell built-ins and commands with non-standard options.
7. Use printf instead of echo
When using echo, the output is sent to standard output (stdout). This means that it can be easily redirected and manipulated. On the other hand, printf sends its output directly to a file descriptor, which makes it more difficult to manipulate.
Additionally, printf allows you to format your output in a way that’s easier to read and understand. For example, you can use printf to add timestamps or log levels to your logs. This makes it much easier to debug issues when they arise.
8. Use curly braces {} around variable names
When you use a variable in a bash script, the shell will try to interpret it as either an environment variable or a command. If you don’t enclose the variable name in curly braces, then the shell may misinterpret your intention and cause unexpected results.
For example, if you have a variable called “my_var” and you want to log its value, you should write:
echo “My var is ${my_var}”
This ensures that the shell interprets the variable correctly and logs the correct value. Without the curly braces, the shell might think you are trying to run a command called “my_var”, which could lead to errors.
9. Use date command for timestamps
The date command is a built-in utility that allows you to easily format the output of timestamps. This makes it easier for you to read and understand log entries, as well as search through them quickly.
The syntax for using the date command in bash scripts is simple:
date +”%Y-%m-%d %H:%M:%S”
This will print out the current timestamp in the following format: YYYY-MM-DD HH:MM:SS. You can also customize this format to suit your needs. For example, if you only need the year and month, you could use the following syntax:
date +”%Y-%m”
10. Use tee command to write logs to stdout
The tee command allows you to write logs to both stdout and a file. This is useful because it allows you to view the output of your script in real-time, while also writing the log to a file for later review. It’s also helpful if you need to debug an issue with your script as you can quickly see what’s happening without having to open up a separate log file.
Using the tee command also helps ensure that all of your logging information is stored in one place, making it easier to search through when needed. Additionally, using the tee command ensures that any errors or warnings are written to the log file, which can be invaluable when troubleshooting issues.