ARG!? and I mean that literally...
what need way validate parameter such function can assume
parameter of particular type, in case, should valid powershell command of description.first try:
ps c:\> function zap { >> param ( >> [validatescript({get-command $_})] >> $cmd >> ) >> if ( $cmd -eq '' ) {'parameter blank'} >> if ( $cmd -eq $null) {'parameter null'} >> write-host "this command: '$cmd'" >> } >> ps c:\> zap zap # 1. should work command: 'zap' ps c:\> zap zappa # 2. should fail zap : cannot validate argument on parameter 'cmd'. "get-command $_" validation script argument value " zappa" did not return true. determine why validation script failed , try command again. @ line:1 char:8 + zap <<<< zappa # 2. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap '' # 3. should fail zap : cannot validate argument on parameter 'cmd'. cannot validate argument on parameter 'name'. argument null o r empty. supply argument not null or empty , try command again. @ line:1 char:8 + zap <<<< '' # 3. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap $null # 4. should fail zap : cannot validate argument on parameter 'cmd'. argument null, empty, or element of argument collectio n contains null value. supply collection not contain null values , try command again. @ line:1 char:8 + zap <<<< $null # 4. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap # 5. should fail parameter null command: '' ps c:\> i have thought parameter no content have failed get-command validation, apparently not. of course if $_ blank get-command succeed, because without parameters returns list of commands. not case command:
get-command ""
so here's second attempt:
ps c:\> function zap { >> param ( >> [validatescript({get-command "$_"})] >> $cmd >> ) >> if ( $cmd -eq '' ) {'parameter blank'} >> if ( $cmd -eq $null) {'parameter null'} >> write-host "this command: '$cmd'" >> } >> ps c:\> zap zap # 1. should work command: 'zap' ps c:\> zap zappa # 2. should fail zap : cannot validate argument on parameter 'cmd'. "get-command "$_"" validation script argument value "zappa" did not return true. determine why validation script failed , try command again. @ line:1 char:8 + zap <<<< zappa # 2. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap '' # 3. should fail zap : cannot validate argument on parameter 'cmd'. cannot validate argument on parameter 'name'. argument null o r empty. supply argument not null or empty , try command again. @ line:1 char:8 + zap <<<< '' # 3. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap $null # 4. should fail zap : cannot validate argument on parameter 'cmd'. argument null, empty, or element of argument collectio n contains null value. supply collection not contain null values , try command again. @ line:1 char:8 + zap <<<< $null # 4. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap # 5. should fail parameter null command: '' ps c:\> but still no luck. let's beef validation code in attempt three:
ps c:\> function zap { >> param ( >> [validatescript({get-command "$_"})] >> [validatenotnullorempty()] >> $cmd >> ) >> if ( $cmd -eq '' ) {'parameter blank'} >> if ( $cmd -eq $null) {'parameter null'} >> write-host "this command: '$cmd'" >> } >> ps c:\> zap zap # 1. should work command: 'zap' ps c:\> zap zappa # 2. should fail zap : cannot validate argument on parameter 'cmd'. "get-command "$_"" validation script argument value "zappa" did not return true. determine why validation script failed , try command again. @ line:1 char:8 + zap <<<< zappa # 2. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap '' # 3. should fail zap : cannot validate argument on parameter 'cmd'. argument null or empty. supply argument not null o r empty , try command again. @ line:1 char:8 + zap <<<< '' # 3. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap $null # 4. should fail zap : cannot validate argument on parameter 'cmd'. argument null or empty. supply argument not null o r empty , try command again. @ line:1 char:8 + zap <<<< $null # 4. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap # 5. should fail parameter null command: '' ps c:\> and still no luck. thing find odd validatenotnullorempty not flag missing parameter, while code in function seems detect condition $null.
so attempt 4 make mandatory parameter. surely work:
ps c:\> function zap { >> param ( >> [parameter(mandatory = $true)] >> [validatescript({get-command "$_"})] >> [validatenotnullorempty()] >> $cmd >> ) >> if ( $cmd -eq '' ) {'parameter blank'} >> if ( $cmd -eq $null) {'parameter null'} >> write-host "this command: '$cmd'" >> } >> ps c:\> zap zap # 1. should work command: 'zap' ps c:\> zap zappa # 2. should fail zap : cannot validate argument on parameter 'cmd'. "get-command "$_"" validation script argument value "zappa" did not return true. determine why validation script failed , try command again. @ line:1 char:8 + zap <<<< zappa # 2. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap '' # 3. should fail zap : cannot validate argument on parameter 'cmd'. argument null or empty. supply argument not null o r empty , try command again. @ line:1 char:8 + zap <<<< '' # 3. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap $null # 4. should fail zap : cannot validate argument on parameter 'cmd'. argument null or empty. supply argument not null o r empty , try command again. @ line:1 char:8 + zap <<<< $null # 4. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap # 5. should fail cmdlet zap @ command pipeline position 1 supply values following parameters: cmd: zap : cannot validate argument on parameter 'cmd'. cannot validate argument on parameter 'name'. argument null o r empty. supply argument not null or empty , try command again. @ line:1 char:8 + zap <<<< # 5. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> well n
ow we're getting somewhere. instead of reporting error when mandatory parameter absent, prompts user value use. that's fine interactive command. function going used in script run user not have better idea give parameter writer of script (me).so, resolve this, seems must include code in function detect absent parameter comparing $null, though have used validatenotnullorempty. fortunately, not need create own version of error message see, can call function recursively so:
ps c:\> function zap { >> param ( >> [validatescript({get-command "$_"})] >> [validatenotnullorempty()] >> $cmd >> ) >> if ( $cmd -eq $null) {zap $null;return} >> write-host "this command: '$cmd'" >> } >> ps c:\> zap zap # 1. should work command: 'zap' ps c:\> zap zappa # 2. should fail zap : cannot validate argument on parameter 'cmd'. "get-command "$_"" validation script argument value "zappa" did not return true. determine why validation script failed , try command again. @ line:1 char:8 + zap <<<< zappa # 2. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap '' # 3. should fail zap : cannot validate argument on parameter 'cmd'. argument null or empty. supply argument not null o r empty , try command again. @ line:1 char:8 + zap <<<< '' # 3. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap $null # 4. should fail zap : cannot validate argument on parameter 'cmd'. argument null or empty. supply argument not null o r empty , try command again. @ line:1 char:8 + zap <<<< $null # 4. should fail + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> zap # 5. should fail zap : cannot validate argument on parameter 'cmd'. argument null or empty. supply argument not null o r empty , try command again. @ line:7 char:34 + if ( $cmd -eq $null) {zap <<<< $null;return} + categoryinfo : invaliddata: (:) [zap], parameterbindingvalidationexception + fullyqualifiederrorid : parameterargumentvalidationerror,zap ps c:\> this works, unfortunately, reports location of error "zap $null" statement in function instead of function called from.
can suggest way use validation (instead of coding) ensure non-mandatory parameter not missing? or, alternately, make mandatory such absense throw error instead of going interactive on me?
al dunbar
it may moot far usage. figure out how things work. i'm more remember need use syntax if understand it's doing.
before write off "syntactic coincidence" consider http://technet.microsoft.com/en-us/library/dd347600.aspx
validatescript validation attribute
validatescript attribute specifies script used
validate parameter value. windows powershell pipes
parameter value script , generates error if the
script returns "false" or if script throws exception.
when use validatescript attribute, parameter value
being validated mapped $_ variable. can
use $_ variable refer parameter value in script.
in following example, value of eventdate parameter
must greater or equal current date.
param
(
[parameter()]
[validatescript({$_ -ge (get-date)})]
[datetime]
$eventdate
)
[string](0..33|%{[char][int](46+("686552495351636652556262185355647068516270555358646562655775 0645570").substring(($_*2),2))})-replace " "
Windows Server > Windows PowerShell
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