Crmgo Blog

Loops.

← Blog

renisans

Loops.

The for-in Loop The for-in statement is designed to sequentially access values listed in a list. Each value in the list is assigned to a variable in turn. The syntax is as follows: Let's consider a small example: After executing the example, a line with its number will appear in the first 5 virtual consoles (terminals). In...

Loops.

for-in loop

The for-in statement is designed to sequentially access values listed in a list. Each value in the list is sequentially assigned to a variable. The syntax is as follows:

for переменная in список_значений
do
  команды
done

Let's consider a small example:

#!/bin/bash
for i in 0 1 2 3 4 #переменной $i будем поочередно присваивать значения от 0 до 4 включительно
do
echo "Console number is $i" >> /dev/pts/$i #Пишем в файл /dev/pts/$i(файл виртуального терминала) строку "Console number is $i"
done #цикл окончен
exit 0

After executing the example, a line with its number will appear in the first 5 virtual consoles (terminals). The variable $i is sequentially assigned values from the list, and the loop operates on the value of this variable.

Loops. while loop

The while loop is more complex than the for-in loop and is used to repeat commands as long as a certain expression is true (return code = 0). The syntax of the statement is as follows:

while выражение или команда возвращающая код возврата
do
  команды
done

Let's consider an example of the loop's operation:

#!/bin/bash
again=yes #присваиваем значение "yes" переменной again
while [ "$again" = "yes" ] #Будем выполнять цикл, пока $again будет равно "yes"
do
echo "Please enter a name:"
read name
echo "The name you entered is $name"

echo "Do you wish to continue?"
read again
done
echo "Bye-Bye"

Note: This post may be AI-assisted and then human-edited. Editorial responsibility: Dmytro Lomaka, Kaltenkirchen.