Shell script parsing 5 ---- loop statements

I. For Loop

For VaR in [LIST]

Do

# Code block

Done

$ VaR is a loop control variable. [LIST] is a set that VaR needs to traverse. The do/done pair contains the loop body. If do and for are written in the same line, you must add ";" before do, for example, for $ VaR in [LIST]; do

For example:

#! /Bin/bash

For day in Sun mon Tue wed Thu Fri Sat

Do

Echo $ day

Done

Execution result:

If the list is contained in a pair of parentheses, it is considered an element. For example

#! /Bin/bash

For day in "Sun mon Tue wed Thu Fri Sat"

Do

Echo $ day

Done

Ii. While and

While [condition]

Do

# Code block

Done

Until [condition]

Do

# Code block

Done

Note: The difference between while and until is that when while is true, until is false.