a - while loop in shell scripts while loop executes its block of commands as long as the given condition remains true syntax
while [ condition ]; do Commands to execute done
[ condition ] is evaluated before each iteration. If the condition evaluates to true, the commands inside the loop are executed. Once the commands finish executing, the condition is re-evaluated. This process continues until the condition becomes false. while [ $count -le 5 ] → The loop continues to execute as long as the condition $count is less than or equal to 5 evaluates to true. you can use the break command to exit the loop prematurely if a certain condition is met. continue command can be used to skip the rest of the current iteration and move directly to the next iteration.
b - until loop in shell scripts until loop is a control flow statement that repeatedly executes a block of code as long as a specified condition evaluates to false. Once the condition becomes true, the loop terminates. syntax
until [condition]; do Commands to execute done
[condition]: The condition that must become true for the loop to exit. until [ "$user_input" == "exit" ]; do → loop will continue executing as long as the condition is false while vs until loop Condition Evaluation: while: Executes as long as the condition is true. until: Executes until the condition becomes true. Typical Use Cases: while: When you know in advance how many times to loop (e.g., iterating over a range). until: When you want to keep looping until a specific condition is met (e.g., waiting for an event).