Bash脚本 - 函数退出时全局变量变为空

Question

信息

我有一个问题，我想从 bash 脚本函数返回一个值（数组或字符串）。

我已经知道以下内容：

• 名为 outputtext=$(functionName) 的 bash 脚本在子 shell 中运行
• bash 函数的作用与“普通”编程语言不同，它只是返回 文本输出
• bash 函数只能返回错误代码作为状态，并且可以通过$? 访问

测试脚本

我现在创建的一个测试脚本来演示我想要做什么，以及为什么我不能直接使用输出

   #!/bin/bash
   declare GLOBAL_VAR
   function callThis(){
      local output="==========================================\n"
      output="$output [START callThis()]\n"
      # For demonstration only - error 5 might be a built-in bash error code, but if caller
      # expects 0/5 they can be handled
      local statusCode=5
      # This variable is empty as soon as it exits the function
      GLOBAL_VAR="Some array value OR text output into GLOBAL_VAR"
      # Because the script has alot of text (echo'd/printf) output, and the function
      # calculates a result (array), I would like to have it as a RESULT
      # for another function.
      output="$output This is some output that will be sent to caller.\n"
      output="$output Test to see if GLOBAL_VAR is assigned:\n"
      output="$output '$GLOBAL_VAR'\n"
      output="$output [END callThis()]\n"
      output="$output ==========================================\n"
      echo -e $output
      return $((statusCode))
   }

   function startHere(){
      OUTPUT=$(callThis)
      STATUS_RESULT=$?
      echo -e "[Text output : $OUTPUT\n]"
      echo -e "[Status Code : $STATUS_RESULT\n]"
      echo -e "[Global VAR in startHere():\n'$GLOBAL_VAR']"
      if [ "$STATUS_RESULT" -eq 5 ]; then
         echo "Success! Status code $STATUS_RESULT found!"
      fi
   }

   echo -e $(startHere)
   echo "Global VAR is now (outside functions): '$GLOBAL_VAR'"

以上结果

我知道 echo -e 并没有给出这个函数的确切输出，除了这个主题

   [Text output :
   ========================================== 
   [START callThis()]
    This is some output that will be sent to caller. 
   Test to see if GLOBAL_VAR is assigned: 
   'Some array value OR text output into GLOBAL_VAR' 
   [END callThis()]
   ========================================== ] 
   [Status Code : 5 ] 
   [Global VAR in startHere(): '']
   Success! Status code 5 found!
   Global VAR is now (outside functions): ''

上面的脚本显示了我想做的大部分事情：我有很长的函数，有计算结果数组，并处理退出代码。

问题

由于它是在调用$(startHere) 时甚至在startHere() 中创建的子shell，所以GLOBAL_VAR 在callThis() 退出后立即为空。

我不知道如何继续，因为我需要另一个函数的值。我该如何解决这个问题？

解决方案

关于我提供的示例，请参阅 @mjrezaee 的解决方案。

原来我并不是所有事情都需要使用子shell$()，大部分时候直接调用函数，输出，全局变量，甚至错误码（返回码）都有. （我不经常使用 bash 脚本）。根据建议，我调整了我的 400 多行脚本，并且能够轻松使用全局变量。

Answer 1

正如我在 cmets 中所说，您可以使用简单的函数调用，对测试代码的简单更改如下：

   #!/bin/bash
   declare GLOBAL_VAR
   function callThis(){
      local output="==========================================\n"
      output="$output [START callThis()]\n"
      # For demonstration only - error 5 might be a built-in bash error code, but if caller
      # expects 0/5 they can be handled
      local statusCode=5
      # This variable is empty as soon as it exits the function
      GLOBAL_VAR="Some array value OR text output into GLOBAL_VAR"
      # Because the script has alot of text (echo'd/printf) output, and the function
      # calculates a result (array), I would like to have it as a RESULT
      # for another function.
      output="$output This is some output that will be sent to caller.\n"
      output="$output Test to see if GLOBAL_VAR is assigned:\n"
      output="$output '$GLOBAL_VAR'\n"
      output="$output [END callThis()]\n"
      output="$output ==========================================\n"
      echo -e $output
      return $((statusCode))
   }

   function startHere(){
      # OUTPUT=$(callThis)
      callThis
      STATUS_RESULT=$?
      # echo -e "[Text output : $OUTPUT\n]"
      echo -e "[Status Code : $STATUS_RESULT\n]"
      echo -e "[Global VAR in startHere(): '$GLOBAL_VAR']"
      if [ "$STATUS_RESULT" -eq 5 ]; then
         echo "Success! Status code $STATUS_RESULT found!"
      fi
   }
   # echo -e $(startHere)
   startHere
   echo "Global VAR is now (outside functions): '$GLOBAL_VAR'"

输出：

==========================================
 [START callThis()]
 This is some output that will be sent to caller.
 Test to see if GLOBAL_VAR is assigned:
 'Some array value OR text output into GLOBAL_VAR'
 [END callThis()]
 ==========================================

[Status Code : 5
]
[Global VAR in startHere(): 'Some array value OR text output into GLOBAL_VAR']
Success! Status code 5 found!
Global VAR is now (outside functions): 'Some array value OR text output into GLOBAL_VAR'

this 也有助于解释其他使用 sub-shell 的方法