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Is there a do-while loop in bash?
I know how to program a while loop in bash:
while [[ condition ]]; do
body
done
Is there a similar construct, but for a do-while loop, where the body is executed at least once irrespective of the while condition?
685
There is no do-while loop in bash. To execute a command first then run the loop, you must either execute the command once before the loop or use an infinite loop with a break condition.
Bash else-if statement is used for multiple conditions. It is just like an addition to Bash if-else statement. In Bash elif, there can be several elif blocks with a boolean expression for each one of them. In the case of the first 'if statement', if a condition goes false, then the second 'if condition' is checked.
Just like && , || is a bash control operator: && means execute the statement which follows only if the preceding statement executed successfully (returned exit code zero). || means execute the statement which follows only if the preceding statement failed (returned a non-zero exit code).
$1 - The first argument sent to the script. $2 - The second argument sent to the script.
while loops are flexible enough to also serve as do-while loops:
while
body
condition
do true; done
For example, to ask for input and loop until it's an integer, you can use:
while
echo "Enter number: "
read n
[[ -z $n || $n == *[^0-9]* ]]
do true; done
This is even better than normal do-while loops, because you can have commands that are only executed after the first iteration: replace true with echo "Please enter a valid number".
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