a=5 while [[ $a -gt 0]] do echo $a let "a-=1" done

This is a bash script that will output the numbers 5 to 1 in descending order.

Here's how it works:

- "a=5" initializes the variable "a" to 5.
- "while [[ $a -gt 0]]" creates a loop that will execute as long as the value of "a" is greater than 0.
- "echo $a" outputs the value of "a" to the console.
- "let "a-=1"" decrements the value of "a" by 1 each time the loop executes.

So the first time through the loop, "a" is 5, which satisfies the condition of the loop, so "5" is output to the console. Then "a" is decremented to 4, and the loop executes again, outputting "4". This process repeats until "a" reaches 0, at which point the loop terminates.

The final output of the script will be:

5
4
3
2
1