The for loop basically iterates over a list , and then executes the given set of commands. .END. What this loop does is take a set of commands into consideration. The until loop is almost equal to the while loop, except that the code is executed while the control expression evaluates to false. OR operator returns true if any of the operands is true, else it returns false. Bash has been one of the most powerful scripting tools. In until loop until the expression is false, i.e. command1 to command3 will be executed repeatedly till condition is true. bash while loop for 5 minutes (define sleep duration as 30 seconds) Here I have created a small script which will run for 5 minutes, and will run a command every 10 seconds. The While loop. The various loops that Bash command has to offer are very useful. You are trying to break from a loop outside a function from inside that function. Bash While Loop is a loop statement used to execute a block of statements repeatedly based on the boolean result of an expression, for as long as the expression evaluates to TRUE. The tow loops: while loop and the until loop are so similar that their syntax is almost the same. While Loops. As the condition becomes false, the execution moves to the next line of code outside of the while loop. Infinite while Loop# The loop which repeats indefinitely and never terminates is infinite loop. The statements from command-1 to command-n are statements executed in a loop until the condition becomes false.eval(ez_write_tag([[728,90],'delftstack_com-medrectangle-3','ezslot_2',113,'0','0'])); Here, initially, num is set to 5. How you can use while loop in bash script is shown in this article by using different examples. An infinite loop is nothing but a sequence of instructions which loops endlessly, either due to the loop having no terminating condition, having one that can never be met, or one that causes the loop to start over. Syntax of while loop: while [condition ] do commands done. Use the false command to set an infinite loop: #!/bin/bash while false do echo "Do something; hit [CTRL+C] to stop!" In this tutorial you have learned: The structure of a while loop in Bash. Bash while Loop continue Syntax while true do [ condition1 ] && continue cmd1 cmd2 done A sample shell script to print number from 1 to 6 but skip printing number 3 and 6 using a while loop : Three types of loops are used in bash programming. It is the expression according to which the loops operate. Most of the time we’ll use for loops or while loops. In a while loop, until the expression is true the loop is iterated as soon as the expression becomes wrong the loop terminates. As it is the exit controlled loop, it keeps on executing given lines of codes. For example, the following 3x10.sh script uses a while loop that will print the first ten multiples of the number three: #!/bin/bash num=1 while [ $num -le 10 ]; do echo $(($num * 3)) num=$(($num+1)) done. Bash while Loop . Now time for the loop that we are all here for, the For loop!! The loop is executed as long as num is greater than or equal to 0. There are also a few statements which we can use to control the loops operation. In the following example, we are using the built-in command : to create an infinite loop. There are 3 basic loop structures in Bash scripting which we'll look at below. bash while loop for 5 minutes (define sleep duration as 30 seconds) Here I have created a small script which will run for 5 minutes, and will run a command every 10 seconds. Create a File Using the Terminal in Linux, Save Files in Vim Before Quitting the Vim Editor, Move Files and Directories in Linux Using Mv Command, Delete Files and Directories in Linux Terminal. Bash while Loop While loops are sort of like a repeating conditional statement. If the condition is true, we execute the statements in the loop. One of the easiest loops to work with is while loops. Conclusion I trust you can start seeing the power of Bash, and especially of for, while and until Bash loops. It is used to exit from a for, while, until, or select loop. : is a shell builtin command. In fact, the loops (specifically for loop in bash) are quite useful. This might be little tricky. We keep printing num in the terminal and decrementing num by 1 in a loop as long as the num value is greater than or equal to 0. in every 0.5 seconds. While loops execute as long as something is true/valid, whereas until loops execute as long as something is 'not valid/true yet'. 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