Loop in Unix // Linux: Loop in Unix // Linux

Loop in Unix // Linux: Loop in Unix // Linux is easier to understand when the core ideas are paired with practical examples. The sections below explain the topic clearly, highlight useful steps, and point out details that can prevent common errors.

A loop is a program that has powerful features, allowing you to repeat a set of commands. In this chapter, you will learn through practical examples of loops contained in shell programs.

While loop
For loop
Until loop
Loop select

You will use different loops based on different situations. As an example,, the while loop will run the command until the given condition remains true, while the until loop will run until the given condition becomes true.

Once you have good program exercises, you will start using the appropriate loop based on the given situation. Here, while and for loops are available in most other program languages such as C, C ++ and PERL etc.

Insert loops in Unix / Linux

All loops support nested concepts, which means you can put a loop inside a similar loop or other loops. This nesting may not limit the maximum number of loops, it depends on your requirements.

Here's an example of nesting a while loop, and in the same way, other loops can be nested according to program requirements.

Insert the while loop in Unix / Linux

It is possible to use a while loop as part of the body of another while loop.

Syntax:

 while command1 ; # Day is a big loss, a lot of money is left due to the fact that the command1 is true while command2 ; # Day is dead long, it is dead in the game because of the command of the command2 is true done

As an example,:

The following is a simple example of loop nesting:

 #! / bin / sh a = 0 while [ "$ a" - lt 10 ] # this is loop1 because b = "$ a" while [ "$ b" - ge 0 ] # this is loop2 do echo - n "$ b " b = ` expr $ b - 1` done echo a = `expr $ a + 1` done

It produces the following result. It is important to remember how echo -n works here. Here -n option allows echo to avoid printing a new character line.

 0 1 0 2 1 0 3 2 1 0 4 3 2 1 0 5 4 3 2 1 0 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0

According to Tutorialspoint

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FAQ

What should you know about insert loops in Unix / Linux?

All loops support nested concepts, which means you can put a loop inside a similar loop or other loops. This nesting may not limit the maximum number of loops, it depends on your requirements.