logger Command: Tutorial & Examples
logger command is a versatile tool in the Linux arsenal that is often overlooked. It is a shell command interface
to the syslog system log module, which allows you to directly add messages into the system log file from
the shell terminal or from within a shell script.
What it does
logger command sends messages to the syslog daemon, which determines where to log the messages based on its
configuration file, typically
/etc/rsyslog.conf depending on the system. This makes it a handy tool for
diagnosing issues and tracking system behavior.
How it works
logger command works by interfacing with the syslog module in the Kernel. When you run the
command, it takes your message, adds a timestamp and other metadata, and passes it to syslog, which files it according
to its configuration.
logger "This is a test message"
What it is used for
logger is used for adding custom messages to system logs. This can be helpful for debugging issues, tracking system
behavior, or adding extra context to existing logs. For example, if you have a script that's causing
a high load issue, you can use
logger to add messages at various points in the script to
track its progress and find the issue.
Why it is important
Understanding and utilizing the
logger command is crucial for effective system administration and troubleshooting. It
provides a simple and efficient way to interact with the system logs, making it easier to diagnose and solve problems.
How to use it and common command line parameters
logger command is straightforward to use. The most basic usage is simply
logger followed by your message.
However, it also supports a number of useful options:
-t, --tagadds a custom tag to your messages.
-p, --prioritysets the priority of the message. This is a combination of the facility and level, for example
-i, --idlogs the process ID with each message.
-s, --stderralso outputs the message to the standard error.
Here's an example using some of these options:
logger -t myscript -p user.info "Script started"
This would log the message "Script started" with the tag "myscript" and a priority of user.info.
Potential problems and pitfalls
logger is a powerful tool, there are a few things to be aware of. Firstly, log files can become very large, and
if not managed properly, they can fill up your disk space. You should set up log rotation to avoid this.
Another potential issue is that if your syslog daemon is not configured correctly, your messages may not be logged where
you expect, or at all. Always check your syslog configuration if you're having issues with
Finally, remember that anyone who can read the log files can see your messages. Don't log sensitive information like passwords or personal data.
logger command is a powerful tool for interacting with your system logs. It's simple to use, but also supports a
range of options for more complex use cases. Whether you're debugging a script or diagnosing a system issue,
can be an invaluable tool in your Linux toolkit.