Until loop in Shell

The while loop is perfect for the situation where you want to execute a set of commands while some conditions are true. Sometimes you need to execute a set of commands until a condition is true, then you need to use a until loop .

Syntax in Unix / Linux

 until command do cac lenh duoc thuc thi toi khi command la true done 

Here the command is estimated. If the value is false , the command is executed. If the command is true , then the command will not be executed and the program will jump to the command line after the done command.

For example in Unix / Linux

Here is a simple example that uses a until loop to display numbers from 0 to 9.

 #!/bin/sh a = 0 until [ ! $a - lt 10 ] do echo $a a = `expr $a + 1` done 

It will produce the following result:

 0 1 2 3 4 5 6 7 8 9 

According to Tutorialspoint

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