Redirection of Linux shell code blocks

Code block redirection refers to redirecting standard or standard output to a file within a block of code, or leaving the default state outside of a block of code, in other words, code block redirection refers to the redirection of standard input or standard output only within the code block. A code block that can be redirected is a while, a until, a for, or a if/then, or even a function.

While redirection

#！ /bin/bash

ls/etc> logs

While ["$filename"! = "RC.D"]

Do

Read filename

Let "count=count+1"

Done < logs #while代码块重定向输入

#测试代码块外部的标准输入是否重定向

echo "Pls, input data:"

Read Test

echo "$test"

The redirect input for the for code block is similar

if [condition]

Then

......

......
Else

......

Fi < filename

Code block redirection increases the flexibility of the shell to a certain extent, allowing a piece of code to handle a file conveniently.