convert "Yes" or "No" to boolean

Question

I want to parse user values contained in .CSV file. I don't want my users to enter "Yes" or "No" but instead enter "True" or "False". In each case I want to convert to the equivalent boolean values: $true or $false. Ideally I would like a default value, so if there's misspelt "Yes or "No" I would return my default value: $true or $false.

Hence, I wondered if there is a neat way of doing this other than

if(){} else (){}

I have problems with your 'misspelling' caveat here. So, you're saying if the user enters 'Yen' that you want it to be $true? What are the conditions? The first letter has to match? — gravity, Mar 29 '16 at 16:51

Ansgar Wiechers · Answer 1 · 2016-03-29T16:56:49.180

6

One way is a switch statement:

$bool = switch ($string) {
  'yes' { $true }
  'no'  { $false }
}

Add a clause default if you want to handle values that are neither "yes" nor "no":

$bool = switch ($string) {
  'yes'   { $true }
  'no'    { $false }
  default { 'neither yes nor no' }
}

Another option might be a simple comparison:

$string -eq 'yes'            # matches just "yes"

or

$string -match '^y(es)?$'    # matches "y" or "yes"

These expressions would evaluate to $true if the string is matched, otherwise to $false.

edited Mar 29 '16 at 16:56

answered Mar 29 '16 at 16:50

Ansgar Wiechers

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1

don't forget the `default` clause – JamesQMurphy Mar 29 '16 at 16:53
1

Using `-ieq` and `-imatch` will make them case-insensitive. – Eris Mar 29 '16 at 17:12
@Eris PowerShell comparison operations are case-insensitive by default. You neet to use `-ceq`/`-cmatch` to make them case-sensitive. – Ansgar Wiechers Mar 29 '16 at 17:19
@Ansgar Thanks so much . I hate typing so the $string match is one I will test out - I think i need to learn regex tho ;-) . Be good if worked with "yes" and "YES" – westerdaled Mar 29 '16 at 17:20
Instead of `'^y(es)?$'`, you could also use `-like 'y*'` – Eris Mar 29 '16 at 17:29
1

`-like 'y*'` would match any string that starts with a `y`. I thought that might be too broad, so I chose to not list this variant. – Ansgar Wiechers Mar 29 '16 at 18:09

score 5 · Answer 2 · answered Mar 29 '16 at 16:47

5

Ah, the magic of powershell functions, and invoke expression.

function Yes { $true }
function No { $false }

$magicBool = & $answer

Note: This is case insensitive, but will not handle misspellings

answered Mar 29 '16 at 16:47

Eris

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It is all fun and games until someone types `rd *`. – beatcracker Mar 30 '16 at 15:05
The OP said they were parsing a file, I'm assuming they have control over the input. – Eris Mar 30 '16 at 16:10

Roman Kuzmin · Answer 3 · 2016-03-29T17:24:13.760

1

If the only possible values are "Yes" and "No" then probably the simplest way is

$result = $value -eq 'Yes'

With misspelled values and the default $false the above will do as well.

With misspelled values and the default $true this will work

$result = $value -ne 'No'

edited Mar 29 '16 at 17:24

answered Mar 29 '16 at 17:17

Roman Kuzmin

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$result = $ForcePasswordChange -ne 'No' seems to be the most elegant solution as I want the default to be $true unless the client explicit requests this. Loads of good suggestions everyone. Thanks – westerdaled Mar 29 '16 at 18:24

score 1 · Answer 4 · answered Jan 05 '17 at 20:27

All of these are valid approaches. If you are looking for a one liner, this will validate it is an acceptable value and set to boolean true if in the 'true' value set. This will also give you a default $false value.

$result = @("true","false","yes","no") -contains $value -and @("true","yes") -contains $value

For a default $true value you would need something like so.

$result = $true

if (@("true","false","yes","no") -contains $value) {
    $result = @("true","yes") -contains $value
}

score 0 · Answer 5 · answered Mar 29 '16 at 16:53

Without a full snippet of your existing code, something like this would probably be an alternative path to take, as opposed to a string of IF statements.

NOTE: This will not handle simple 'Y' or 'N' input, but is case insensitive. So, you should be able to see 'yes' or 'YES' working, as well.

$myVar = Read-Host 'What is your answer?'
switch ($myVar)
{
  Yes {$myVarConverted = $true; break}
  True {$myVarConverted = $true; break}
  No {$myVarConverted = $false; break}
  False {$myVarConverted = $false; break}
  default {"Invalid Input"; break}
}
Write-Host $myVarConverted

Please see my additional comment on your question about the 'misspelling' caveat. That's difficult to code around without specific restrictions or requirements.

score 0 · Answer 6 · answered Mar 29 '16 at 18:06

0

Here's the way I do Yes-No answers:

function ask-user
{
   [CmdletBinding()]
   Param(
      [Parameter(Mandatory=$true)]
      [string] $question
   )
   Process
   {  $answer = read-Host $question
      if ("yes" -match $answer) {$true}
      elseif ("no" -match $answer) {$false}
      else {ask-user $question}
   }
}

You can easily substitute true and false for yes and no.
This one is case insensitive, and will match valid abbreviations. (Y or N). In the case of misspellings, it asks again. Yeah, I could have done it without recursion, but I'm lazy.

answered Mar 29 '16 at 18:06

Walter Mitty

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I see what you are doing, you force a "yes" or "no" else ask again . I might upper case it so that is handled as well. Good suggestion. – westerdaled Apr 07 '16 at 15:21
It's case insensitive, because that's how -match works. I've tried it with capital Y or N. – Walter Mitty Apr 07 '16 at 19:16

score 0 · Answer 7 · answered Nov 18 '17 at 12:45

These are great solutions above, but let me just say that this whole topic just proves the vast shortcomings of Powershell...

  [System.Convert]::ToBoolean("False") -eq $true ? 
  [System.Convert]::ToBoolean("0") -eq $true ?

Really? Give me a f--kin break.

score 0 · Answer 8 · answered Apr 28 '22 at 10:47

0

For me :-

Function convert2Bool($this) { return ($("False","0","","N","No",'$False',"Off") -notcontains [string]$this) }

can adjust if you don't want $null blank-string going to $false, else fine.

answered Apr 28 '22 at 10:47

SimonTi

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convert "Yes" or "No" to boolean

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