Скачать или смотреть How to Remove IP Addresses from a Text File Using Awk

Discover how to efficiently remove IP addresses from a text file using `awk`, along with a step-by-step explanation of the process.
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How to Remove IP Addresses from a Text File Using Awk

In today's digital landscape, managing and modifying text files is a common task that many developers and system administrators face. One specific challenge that might arise is the need to remove certain IP addresses from a list in a text file based on entries from another file. In this post, we will discuss a clear and concise method to achieve this using the awk command in a Linux environment.

The Problem

You have two files: ips.yaml and result.txt. Your goal is to remove all instances of the IP addresses listed in ips.yaml from the result.txt file. Let's take a closer look at the contents of each file.

Example Content of The Files

ips.yaml:

[[See Video to Reveal this Text or Code Snippet]]

result.txt:

[[See Video to Reveal this Text or Code Snippet]]

Your desired output for result.txt after removal of the specified IP addresses is as follows:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

To perform this operation efficiently, we will use the awk command. Below is the command that can achieve this task:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Command

Let’s break down the above awk command to understand how it functions:

Reading the YAML File:

FNR==NR checks if we are processing the first file (ips.yaml).

The condition /^ + / looks for lines that start with spaces.

ips[$2] creates an associative array (hashmap) where the keys are the IP addresses listed in ips.yaml.

Processing the Result File:

The line match($0,/External_Networks=(\S+ )/,arr) checks if the current line matches the pattern External_Networks= followed by any non-space characters (which will be the IP). If it matches, it stores the IP in the arr array.

The next condition (arr[1] in ips) checks if the captured IP exists in the ips array. If so, it skips printing that line.

Printing the Relevant Lines:

The conditions (/^+ -/) || (/^|/) are used to detect lines that start with + or |, which are part of the table structure in result.txt.

If any of these conditions are met, the line is printed.

Conclusion

By executing the awk command provided, you will successfully remove the specified IP addresses from your result.txt file. The use of awk greatly simplifies the task and allows you to efficiently filter through text based on specified criteria.

Now you have the tools to manage your text files better. Feel free to adapt the script according to your needs and explore more powerful text processing utilities in your workflows!