Coding⏱️ 3 min read📅 2026-06-19

How to Fix: I want to get a count of unique entries in the Apache error logs on

Find unique Apache error messages and their counts using built-in tools.

Quick Answer: Use sed to extract error lines, sort for uniqueness, and xargs with grep to count occurrences.

To troubleshoot Apache error logs and identify unique error messages, you can use a combination of built-in tools such as `cut`, `find`, `grep`, and `sed`. This guide will walk you through a step-by-step process to achieve this using these tools.

The goal is to create a script that provides a count of the different unique lines in your Apache error logs, along with their frequency. We'll use existing scripts as a starting point and modify them to produce the desired output.

🔍 Why This Happens

  • Apache error logs often contain repeated error messages due to various reasons such as misconfigured server settings or incorrect file permissions.
  • This issue can be frustrating for system administrators, but there are steps you can take to identify and resolve the problem using built-in tools on your Linux system.

🛠️ Step-by-Step Verified Fixes

Using `sed` to extract error messages

  1. Step 1: First, use `sed` to extract the error message from each log entry. The command is: `sed -e 's/\[.*\(.*\) / /g' error.sml.log`. This will create a new file containing each error message on a separate line.
  2. Step 2: Next, pipe the output to `sort` and remove duplicates using `-u`: `sed -e 's/\[.*\(.*\) / /g' error.sml.log | sort -u`. This will produce a list of unique error messages.

Using `cut`, `grep`, and `xargs` to format the output

  1. Step 1: Now, use `cut` to extract only the first part of each line (i.e., before the first space): `sed -e 's/\[.*\(.*\) / /g' error.sml.log | cut -d' ' -f1`. This will produce a list of unique error messages without any extra characters.
  2. Step 2: Next, pipe the output to `grep` and count the occurrences of each line: `sed -e 's/\[.*\(.*\) / /g' error.sml.log | cut -d' ' -f1 | grep -oc {} error.sml.log`. This will produce a list with the count of occurrences for each error message.

✨ Wrapping Up

To achieve the desired output, combine steps from both methods: `sed -e 's/\[.*\(.*\) / /g' error.sml.log | cut -d' ' -f1 | grep -oc {} error.sml.log | sort -u`. This will produce a list of unique error messages along with their frequency, formatted as shown in the example output.

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