Detect whether the file exists or not with Bash
Introduction
Bash is a powerful and popular command-line shell used in many operating systems, including Linux and macOS. It comes with a variety of built-in commands and features that make it an excellent tool for automation and scripting tasks. In this blog post, we will discuss how to detect whether a file exists or not using Bash.
TL;DR
#!/usr/bin/env bash
if [[ -f filename ]]; then
echo 'file exist'
else
echo 'file not exist'
fi
Testing for File Existence
One of the most common tasks in Bash scripting is to test if a file exists or not. The test command, also known as [, is used to check file existence. The syntax of the test command is as follows:
test -e FILENAME
Here, -e is an option that tests for the existence of the file FILENAME. If the file exists, the test command returns a status of 0, which means the file exists. If the file does not exist, the test command returns a non-zero status, which means the file does not exist.
Alternatively, you can use the following syntax to test for file existence:
[ -e FILENAME ]
This command is equivalent to the test command. You can also use other options with the test command to test for file existence. For example, the -f option tests for the existence of a regular file, and the -d option tests for the existence of a directory.
Using Short-Circuit Evaluation
Another way to check for file existence is to use short-circuit evaluation. Short-circuit evaluation is a technique used in Bash scripting to evaluate logical expressions in an efficient way. In short-circuit evaluation, if the first condition of a logical expression is true, the rest of the expression is not evaluated.
Here’s an example of using short-circuit evaluation to test for file existence:
[ -e FILENAME ] && echo "File exists"
In this command, the test command is used to test for file existence. If the file exists, the echo command is executed and prints “File exists” to the console.
Conclusion
In conclusion, detecting whether a file exists or not is an essential task when working with Bash scripting. You can use the test command or short-circuit evaluation to test for file existence. By mastering these techniques, you can write more efficient and powerful Bash scripts.