Text processing is a common task in data analysis, where formatting and manipulating text files efficiently can often save a substantial amount of time. In this tutorial, we’ll focus on a frequent scenario where you need to merge lines of a text file in pairs. This can be especially handy when dealing with records, list items, or even code snippets that need to be consolidated. We will craft a Bash script that takes a filename as an argument and then merges its lines in pairs.
Setting Up Your Workspace
Open your preferred text editor and create a new file called merge_lines.sh. This will be your script file.
Script Content
Enter the following lines into merge_lines.sh:
#!/bin/bash
# Check for the presence of an argument
if [ "$#" -ne 1 ]; then
echo "Usage: $0 <filename>"
exit 1
fi
# Check if the file exists
if [ ! -f "$1" ]; then
echo "Error: File not found."
exit 1
fi
# Read the file and merge lines in pairs
awk 'NR%2{printf "%s ",$0;next;}1' "$1"
Making the Script Executable
Run the following command in your terminal to make the script executable:
chmod +x merge_lines.sh
Testing the Script with Real Data
To thoroughly test our script, we’ll create a sample text file with the following contents. Open a new file named sample.txt and insert the following lines:
Line1
Line2
Line3
Line4
Line5
Line6
Save and close sample.txt.
Now, run the script by passing sample.txt as an argument:
./merge_lines.sh sample.txt
The expected output should display the lines of sample.txt merged in pairs:
Line1 Line2
Line3 Line4
Line5 Line6
The script starts by checking if exactly one argument (the filename) is provided.
It then checks whether the file exists and is a regular file.
The awk command reads the file. NR%2 checks if the record number is odd. If it is, awk prints the line without a newline and reads the next line. When it encounters an even line number, it performs the default action, which is to print the line with a newline character, thus merging every two lines.
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