Log Analysis Script: Analyzes Log Files to Identify Trends or Potential Issues

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You’ve finally made it to bash log analysis script. Here’s a tutorial on analyzing log files to identify trends or potential issues using a bash shell script.

1. Open a text editor and create a new file.

2. Add the following code to the file:

#!/bin/bash

# Location of log file
log_file="path/to/log.txt"

# Create a backup of the log file
cp "$log_file" "$log_file".bak

# Sort the log file by date
sort -k 4 -n "$log_file".bak > "$log_file"

# Use awk to analyze the log file and print results
echo "Top 10 most frequent IP addresses:"
awk '{print $1}' "$log_file" | sort | uniq -c | sort -nr | head -10

echo "Top 10 most frequent error codes:"
awk '{print $9}' "$log_file" | sort | uniq -c | sort -nr | head -10

Explanation:

  • The first line specifies the interpreter to be used, in this case, the bash shell.
  • The log_file variable holds the location of the log file to be analyzed. Replace path/to/log.txt with the actual path to your log file.
  • The cp “$log_file” “$log_file”.bak command creates a backup of the log file.
  • The sort -k 4 -n “$log_file”.bak > “$log_file” command sorts the log file by the fourth column, which is typically the date. The -n option is used for numerical sorting, and the -k option specifies the sort key.
  • The awk command is used to analyze the log file and extract information. The ‘{print $1}’ “$log_file” command prints the first column of the log file, which is typically the IP address. The sort and uniq -c commands are used to count the frequency of each IP address, and the sort -nr command sorts the results in descending order by frequency. The head -10 command is used to print the top 10 results.
  • Similar to the IP address analysis, the error code analysis prints the 9th column of the log file using awk ‘{print $9}’ “$log_file”, counts the frequency of each error code, sorts the results in descending order by frequency, and prints the top 10 results using the head -10 command.

3. Save the file with a .sh extension, for example, log_analysis.sh.

4. Make the script executable by running the following command in the terminal:

chmod +x log_analysis.sh

5. Run the script by executing the following command:

./log_analysis.sh

This script will sort the log file by date and analyze it to identify the top 10 most frequent IP addresses and error codes. You can modify the script to analyze other aspects of the log file as needed.

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