Learn how to merge two text files using a shell script, ensuring no duplicate lines appear in the final output. Simple and efficient method for clean data consolidation.

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Merging Two Text Files Without Repeating Lines Using Shell Script

Introduction

In the world of data processing and manipulation, merging files is a common requirement. This task becomes particularly interesting when we want to combine two text files while ensuring that no lines are repeated in the final output. This can be useful for various applications such as log file management, data analysis, and more. In this guide, we will explore how to create a shell script that accomplishes this task efficiently.

Understanding the Problem

When merging two text files, we often encounter duplicate lines. For instance, if both files contain the same line, we want that line to appear only once in the final merged output. This requirement encourages us to consider using shell commands that can filter out duplicates effectively.

Shell Script Solution

To merge two text files without repeating lines, we can leverage basic Unix commands such as cat and sort. The cat command is used to concatenate files, while the sort command can help in sorting and removing duplicates. The uniq command can also be employed to eliminate duplicate lines after sorting.

Step-by-Step Guide

Let’s create a shell script that performs the merging of two text files without repeating lines. Follow the steps below:

#!/bin/bash
# This script merges two text files without repeating lines.

# Checking if the correct number of arguments is provided
if [ "$#" -ne 2 ]; then
    echo "Usage: $0 file1.txt file2.txt"
    exit 1
fi

# Assigning input files to variables
file1=$1
file2=$2
output_file="merged_output.txt"

# Merging files and removing duplicates
cat "$file1" "$file2" | sort -u > "$output_file"

echo "Merged file created: $output_file"

Script Explanation

In the script above, we start by checking if exactly two arguments (the two files to merge) are provided. If not, the script will display a usage message and exit. We then assign the input file names to variables for easier reference.

Using the cat command, we concatenate the contents of the two files. The output is then piped into the sort command with the -u option, which sorts the lines and removes duplicates in one go. Finally, the result is redirected into a new file called merged_output.txt.

Testing the Script

To test the script, save it as merge_files.sh and give it executable permissions using the command chmod +x merge_files.sh. You can then run the script by providing two text files:

./merge_files.sh file1.txt file2.txt

After executing the script, check the merged_output.txt file to ensure it contains the combined content of the two files without any duplicate lines.

Conclusion

This simple yet effective shell script demonstrates how to merge two text files while eliminating duplicate lines. The use of cat, sort, and uniq commands showcases the power of Unix tools in text processing. By following the steps outlined in this guide, you can easily adapt this script for various use cases in file management and data handling.

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