shell if and

In shell scripting, the `if` statement is used to perform conditional execution of commands. It allows you to test conditions and execute different sets of commands based on the result of the condition.

The basic syntax of the `if` statement in shell scripting is as follows:

if [ condition ]
then
    # commands to be executed if the condition is true
else
    # commands to be executed if the condition is false
fi

The `condition` can be a comparison between values, the result of a command, or any expression that evaluates to either true or false. Some commonly used operators for conditions are `-eq` (equal), `-ne` (not equal), `-gt` (greater than), `-lt` (less than), `-ge` (greater than or equal to), and `-le` (less than or equal to).

For example, let's say we want to check if a variable `num` is greater than 10. The corresponding `if` statement would look like this:

if [ $num -gt 10 ]
then
    echo "The number is greater than 10"
else
    echo "The number is less than or equal to 10"
fi

This is just a simple example, and you can have more complex conditions and multiple `elif` statements as well.