Shell 脚本中的字符串连接错误 [英] Error in string Concatenation in Shell Scripting

问题描述

我是 Shell 脚本的初学者.

I am beginner to Shell scripting.

我使用了一个变量来存储值 A="MyScript".我尝试在后续步骤 $A_new 中连接字符串.令我惊讶的是它不起作用，$A.new 起作用了.

I have used a variable to store value A="MyScript". I tried to concatenate the string in subsequent steps $A_new. To my surprise it didn't work and $A.new worked.

你能帮我理解这些细节吗?

Could you please help me in understanding these details?

谢谢

推荐答案

变量名可以包含字母(a 到 z 或 A 到 Z)、数字(0 到 9)或下划线字符(_).

The name of a variable can contain letters ( a to z or A to Z), numbers ( 0 to 9) or the underscore character ( _).

Shell 不需要像 C、C++ 或 java 这样的编程语言中的任何变量声明.因此，当您编写 $A_new shell 时，将 A_new 视为一个变量，您尚未为其分配任何值，因此它为空.

Shell does not require any variable declaration as in programming languages as C , C++ or java. So when you write $A_new shell consider A_new as a variable, which you have not assigned any value therefore it comes to be null.

要实现您提到的用途，请使用:${A}_new

To achieve what you mentioned use as : ${A}_new

在$ 符号后将变量名括在大括号中以避免这种情况始终是一个好习惯.

Its always a good practice to enclose variable names in braces after $ sign to avoid such situation.

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