Setting a global PowerShell variable from a function where the global variable name is a variable passed to the function

Question

I need to set a global variable from a function and am not quite sure how to do it     Set variables  global var1  global var2  global var3  function foo   a   b   c          Add  a and  b and set the requested global variable to equal to it      c    a    b     Call the function   foo 1 2  global var3   End result    global var3 is set to 3  Or if I called the function like this   foo 1 2  global var2   End result    global var2 is set to 3  I hope this example makes sense  The third variable passed to the function is the name of the variable it is to set

User · Answer

As simple as    A  1  function changeA2       global A  0   changeA2  A

User · Answer

I ran across this question while troubleshooting my own code   So this does NOT work      myLogText      function AddLog   Message         myLogText      Message    AddLog   Hello   Write-Host  myLogText   This APPEARS to work  but only in the PowerShell ISE    myLogText      function AddLog   Message         global myLogText      Message    AddLog   Hello   Write-Host  myLogText   This is actually what works in both ISE and command line    global myLogText      function AddLog   Message         global myLogText      Message    AddLog   Hello   Write-Host  global myLogText

User · Answer

For me it worked   function changeA2       global A  0   changeA2  A

User · Answer

You ll have to pass your arguments as reference types     First create the variables  note you have to set them to something   global var1    null  global var2    null  global var3    null   The type of the reference argument should be of type  REF  function foo   a   b   REF  c          add  a and  b and set the requested global variable to equal to it       Note how you modify the value       c Value    a    b     You can then call it like this  foo 1 2  REF  global var3

User · Answer

The first suggestion in latkin s answer seems good  although I would suggest the less long-winded way below   PS c  temp gt   global test  one   PS c  temp gt   test one  PS c  temp gt  function changet     global test  two    PS c  temp gt  changet  PS c  temp gt   test two   His second suggestion however about being bad programming practice  is fair enough in a simple computation like this one  but what if you want to return a more complicated output from your variable  For example  what if you wanted the function to return an array or an object  That s where  for me  PowerShell functions seem to fail woefully  Meaning you have no choice other than to pass it back from the function using a global variable  For example   PS c  temp gt  function changet  byte  a  byte  b  byte  c    global test     a  b   c   a  c     PS c  temp gt  changet 1 2 3  PS c  temp gt   test 3 3 4  PS C  nb gt   test 2  4   I know this might feel like a bit of a digression  but I feel in order to answer the original question we need to establish whether global variables are bad programming practice and whether  in more complex functions  there is a better way   If there is one I d be interested to here it

User · Answer

zdan  Good answer  I d improve it like this     I think that the closest you can come to a true return value in PowerShell is to use a local variable to pass the value and never to use return as it may be  corrupted  by any manner of output situations  function CheckRestart  REF  retval          Some logic      retval Value    true    bool  restart    false CheckRestart   REF  restart  if    restart         Restart-Computer -Force     The  restart variable is used either side of the call to the function CheckRestart making clear the scope of the variable  The return value can by convention be either the first or last parameter declared  I prefer last

User · Answer

You can use the Set-Variable cmdlet   Passing  global var3 sends the value of  var3  which is not what you want   You want to send the name    global var1    null  function foo   a   b   varName       Set-Variable -Name  varName -Value   a    b  -Scope Global    foo 1 2 var1   This is not very good programming practice  though   Below would be much more straightforward  and less likely to introduce bugs later    global var1    null  function ComputeNewValue   a   b        a    b     global var1   ComputeNewValue 1 2

[powershell] Setting a global PowerShell variable from a function where the global variable name is a variable passed to the function

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