How to check the existence of a file or directory in Bash?

In Bash, you can use the test command or the [ command (which is a synonym for test) to check the existence of a file or directory. Here are a few methods:

Using the -e option with the [ command or the test command:

if [ -e "/path/to/file" ]; then
    echo "File exists"
else
    echo "File does not exist"
fi

Using the -f option to check if a file exists:

if [ -f "/path/to/file" ]; then
    echo "File exists"
else
    echo "File does not exist"
fi

Using the -d option to check if a directory exists:

if [ -d "/path/to/directory" ]; then
    echo "Directory exists"
else
    echo "Directory does not exist"
fi

Using the [[ command, which is an extended version of [ command:

if [[ -e "/path/to/file" ]]; then
    echo "File exists"
else
    echo "File does not exist"
fi

Note that you need to replace "/path/to/file" or "/path/to/directory" with the actual file or directory path you want to check.