bash 从linux bash中的函数分配局部变量一个新值
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assign local variable from function in linux bash a new value
提问by Wolfgang Adamec
I have a linux bashscript with a function:
我有一个linux bash带有函数的脚本：
myfunctiona ()
{
local MYVAR1="one"
local MYVAR2="two"
echo $MYVAR1
# The line beneath is the line in question!
local MYVAR1=$MYVAR1$MYVAR2
}
When I want to give the LOCALvariable MYVAR1in the function myfunctionaa new value, do I have to write
当我想给函数中的LOCAL变量一个新值时，我是否必须写MYVAR1myfunctiona
local MYVAR1=$MYVAR1$MYVAR2
or can I also write
或者我也可以写
MYVAR1=$MYVAR1$MYVAR2
With the second line without "local" do I create a global variable with the same name?
对于没有“local”的第二行，我是否创建了一个同名的全局变量？
回答by Geoff Williams
Once you've defined a local variable you can assign it normally, like this:
定义局部变量后，您可以正常分配它，如下所示：
#!/bin/bash
myfunctiona ()
{
local MYVAR1="one"
local MYVAR2="two"
echo $MYVAR1
# The line beneath is the line in question!
local MYVAR1=$MYVAR1$MYVAR2
MYVAR1="FOO"
echo $MYVAR1
}
myfunctiona
echo "global" $MYVAR1
which gives the output:
这给出了输出：
one
FOO
global
- As you can see attempting to access the variable from global scope returns null
- 如您所见，尝试从全局范围访问变量返回 null
HTH
HTH
回答by Saucier
The correct way to do it would be:
正确的做法是：
MYVAR1="${MYVAR1}${MYVAR2}"
The braces are usually used when you concatenate variables. Use quotes.
连接变量时通常使用大括号。使用引号。
The variable is still local since you reassigned its value within the scope of the function. An example:
该变量仍然是本地的，因为您在函数范围内重新分配了它的值。一个例子：
#!/usr/bin/env bash
_myFunction()
{
local var_1="one"
local var_2="two"
local -g var_3="three" # The -g switch makes a local variable a global variable
var_4="four" # This will be global since we didn't mark it as a local variable from the start
var_1="${var_1}${var_2}"
echo "Inside function var_1=${var_1}"
echo "Inside function var_2=${var_2}"
echo "Inside function var_3=${var_3}"
echo "Inside function var_4=${var_4}"
}
_myFunction
echo "Outside function var_1=${var_1}"
echo "Outside function var_2=${var_2}"
echo "Outside function var_3=${var_3}"
echo "Outside function var_4=${var_4}"
This results in:
这导致：
$ ./script
Inside function var_1=onetwo
Inside function var_2=two
Inside function var_3=three
Inside function var_4=four
Outside function var_1=
Outside function var_2=
Outside function var_3=three
Outside function var_4=four
回答by user3004356
You can give this way, but as Ube said for concatenation you need to give like that -
你可以这样给，但正如宇部所说的串联，你需要这样给——
MYVAR1="$MYVAR1$MYVAR2";
Even this works for concatenation
即使这也适用于串联
