About
What is a function in a language grammar ? in Powershell
A function is a special type of command.
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Syntax
function [<scope:>]<name> [([type]$parameter1[,[type]$parameter2])]
{
param([type]$parameter1 [,[type]$parameter2])
dynamicparam {<statement list>}
begin {<statement list>}
process {<statement list>}
end {<statement list>}
}
Simple
function <function-name> {statements}
Example: finds all .jpg files in the current user's directories that were changed after the start date.
function Get-NewPix
{
$start = get-date -month 1 -day 1 -year 2010
$allpix = get-childitem -path $env:userprofile\* -include *.jpg -recurse
$allpix | where {$_.lastwritetime -gt $start}
}
Param
Definition
function md5sum {
param
(
[Parameter(Mandatory=$true, HelpMessage='The file containing the hash.')]
[string]$file
)
echo "Checking if required packages are present and valid..."
foreach ($line in (Get-Content $file)) {
................
}
}
md5sum -file checksum.txt
Check
If the parameters is not mandatory, you can check if it's passed with the following command
if (!($PSBoundParameters.ContainsKey('file'))){
Write-Host "The (file) parameter was not given"
} else {
Write-Host "The (file) parameter was given"
}
Return
Same behavior than bash: All output is captured, and returned
This syntax are the same:
$a
return
# is equivalent to
return $a
Management
List
Get-Command -CommandType Function
Write
about_Functions: Describes how to create and use functions in Windows PowerShell
get-help about_Functions
Help
get-help function-name
- Command based
To create comment-based help for a function, the comments must be placed at the beginning or end of the function body or on the lines preceding the function keyword. get-help about_Comment_Based_Help
# Comment-Based Help for Functions
- XML-Based. See Powershell - Cmdlet