How Read File Line By Line Bash

Shell Programming

Hey there, fellow tech enthusiasts! Today, I want to delve into the world of file handling in the bash scripting language. Specifically, I’ll be covering how to read a file line by line in bash. Whether you’re a seasoned coder or just starting out, understanding this process is essential for manipulating data and automating tasks within the command line. So, let’s dive into the nitty-gritty details of reading files line by line in bash!

Getting Started: Why This Matters

Before we jump into the code, let’s take a moment to understand why reading a file line by line is important. In my experience, this functionality is incredibly useful for processing large datasets, log files, or any text-based data. By accessing each line individually, we can perform operations, extract specific information, or even make modifications as needed.

The Bash Script: Reading Line by Line

Now, let’s get down to the coding part. In bash, we have a few different methods for achieving this, but I’ll focus on using the while loop combined with the read command.


# Check if the file exists
if [ -f “myFile.txt” ]; then
# Open the file for reading
while IFS= read -r line; do
# Process the current line
echo “Current Line: $line”
# Add your custom logic here
done < "myFile.txt" else echo "File not found" fi ```

Let’s break down this script. First, we check if the file “myFile.txt” exists using the conditional if [ -f "myFile.txt" ]; then. If the file exists, we enter the while loop. Within this loop, the read command is used to read each line from the file, and then we have the opportunity to process that line or perform any custom logic. Once the end of the file is reached, the loop exits.

Understanding the Code

With the read command, IFS= is used to prevent leading and trailing whitespace from being trimmed off, and -r is used to ensure that backslashes within the text do not act as escape characters. These are important considerations that ensure our file is processed accurately.

Putting it into Practice

Now, let’s put this code into action. Consider a scenario where you have a log file containing various entries, and you want to filter out lines containing a specific keyword. With the ability to read the file line by line, you can easily achieve this task by adding conditional checks within the while loop.


So, there you have it! We’ve explored the significance of reading files line by line in bash and dissected the code required to accomplish this task. The flexibility and power that this functionality provides are truly remarkable, opening doors to a wide range of automation and data processing possibilities. I hope this article has shed light on the intricacies of file handling in bash, and I encourage you to experiment with this concept in your own projects. Happy coding!