File Operations in Shell Scripting: 3 Practical Examples

Introduction

File operations in shell scripting are essential for automating tasks related to file management, such as creating, modifying, and deleting files. This can streamline workflows and enhance productivity. Below are three practical examples of file operations in shell scripting that showcase different functionalities.

Example 1: Creating and Writing to a File

In scenarios where you need to generate logs or configuration files, creating and writing to a file is a common task. This example demonstrates how to create a new text file and write some initial content into it.

## Create a new file and write content to it
FILE="example.txt"
echo "This is a sample text file." > $FILE
echo "This file contains examples of file operations in shell scripting." >> $FILE

echo "File created and content written successfully."

After executing this script, you will have a file named example.txt containing the specified text. The > operator creates the file and writes the first line, while >> appends the second line.

Notes:

• If example.txt already exists, using > will overwrite it. To avoid accidental data loss, always double-check before executing the script.

Example 2: Reading Contents of a File

Reading contents from files is a crucial operation when you need to process data or retrieve configurations. The following example illustrates how to read a file’s contents line by line and display them on the terminal.

## Read contents of a file and display them
FILE="example.txt"
if [ -f $FILE ]; then
    while IFS= read -r line; do
        echo "Line: $line"
    done < $FILE
else
    echo "File does not exist."
fi

In this example, we first check if example.txt exists. If it does, the script reads it line by line, outputting each line with a prefix. If the file does not exist, a message is displayed.

Notes:

• The IFS= and read -r combination ensures that leading/trailing whitespace is preserved and backslashes are treated literally.

Example 3: Deleting a File

In situations where temporary files or logs need to be cleaned up, deleting files is necessary. This example shows how to remove a specified file safely.

## Delete a specified file
FILE="example.txt"
if [ -f $FILE ]; then
    rm $FILE
    echo "File '$FILE' deleted successfully."
else
    echo "File '$FILE' does not exist."
fi

This script checks if example.txt exists and deletes it if found. A confirmation message is printed afterward to inform the user of the deletion.

Notes:

• Be cautious with the rm command, as it permanently deletes files without moving them to a recycle bin. Always ensure you are targeting the correct file.