perl do while loop-IGI

The do-while loop is another looping construct in Perl that is similar to the while loop. The main difference is that the do-while loop always executes the code block at least once, regardless of whether the condition is true or false.

Here's the basic syntax of the do-while loop in Perl:

refe‮‬r to:theitroad.com

do {
    # block of code to be executed repeatedly
} while (condition);

The loop will continue to execute as long as the condition is true. However, unlike the while loop, the condition is checked at the end of each iteration, after the code block has been executed at least once. If the condition is false, the loop will terminate and execution will continue with the next statement after the loop.

Here's an example of a do-while loop that prints the numbers from 1 to 10:

my $i = 1;
do {
    print "$i\n";
    $i++;
} while ($i <= 10);

In this example, the variable $i is initialized to 1. The code block within the do statement prints the value of $i and increments $i by 1. The loop continues as long as $i is less than or equal to 10. Because the do statement always executes the code block at least once, the value 1 will be printed even if the condition is initially false.

You can use any valid Perl expression as the condition in a do-while loop, just like in a while loop. For example, you can use a comparison operator (<, <=, >, >=, ==, !=) to test a variable against a constant, or you can use a logical operator (&&, ||, not) to combine multiple conditions.

Here's an example of a do-while loop that reads input from the user until the user enters a blank line:

print "Enter some text (or a blank line to exit):\n";
do {
    my $line = <STDIN>;
    chomp $line;
    if ($line eq '') {
        last; # exit the loop if the user entered a blank line
    }
    print "You entered: $line\n";
} while (1);

In this example, the do statement reads input from the user using the <STDIN> filehandle, which reads input from the standard input stream (usually the keyboard). The chomp function is used to remove the newline character from the end of the input. If the user enters a blank line, the last statement is used to exit the loop. Otherwise, the input is printed back to the user. The loop will continue to execute until the user enters a blank line. Because the condition is always true (1), the loop will execute at least once even if the user enters a blank line initially.

tutorial

perl do while loop