How to check if a file is empty in a shell script is a common question among users who work with scripts on Unix-like systems. Checking the emptiness of a file is essential for various reasons, such as ensuring that a file has been successfully created or verifying that a process has not produced any output. In this article, we will discuss different methods to check if a file is empty in a shell script.
One of the simplest ways to check if a file is empty is by using the `-s` flag with the `test` command. The `-s` flag checks if the file exists and has a size greater than zero. If the file is empty, the `test` command will return a false result, which can be interpreted as the file being empty.
Here’s an example of how to use the `-s` flag to check if a file is empty:
“`bash
!/bin/bash
file_path=”/path/to/your/file.txt”
if [ -s “$file_path” ]; then
echo “The file is not empty.”
else
echo “The file is empty.”
fi
“`
In the above script, we check if the file `/path/to/your/file.txt` is not empty by using the `-s` flag. If the file has a size greater than zero, the script will output “The file is not empty.” Otherwise, it will output “The file is empty.”
Another method to check if a file is empty is by using the `wc` command, which counts the lines, words, and bytes in a file. By passing the `-l` flag to `wc`, we can count the number of lines in the file. If the file is empty, `wc` will return a count of zero.
Here’s an example of how to use `wc` to check if a file is empty:
“`bash
!/bin/bash
file_path=”/path/to/your/file.txt”
line_count=$(wc -l < "$file_path") if [ "$line_count" -gt 0 ]; then echo "The file is not empty." else echo "The file is empty." fi ``` In this script, we use `wc -l` to count the number of lines in the file. If the line count is greater than zero, the file is not empty, and the script outputs "The file is not empty." Otherwise, it outputs "The file is empty." Both methods are effective for checking if a file is empty in a shell script. Choose the one that best suits your needs and preferences.
