wirte function in powershell

https://github.com/dahlbyk/posh-git/blob/master/src/Utils.ps1#L102

https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_functions?view=powershell-6

https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_functions_advanced_parameters?view=powershell-6

function Add-PoshGitToProfile {
    [CmdletBinding(SupportsShouldProcess)]
    param(
        [Parameter()]
        [switch]
        $AllHosts,

        [Parameter()]
        [switch]
        $AllUsers,

        [Parameter()]
        [switch]
        $Force,

        [Parameter(ValueFromRemainingArguments)]
        [psobject[]]
        $TestParams
    )

    if ($AllUsers -and !(Test-Administrator)) {
        throw 'Adding posh-git to an AllUsers profile requires an elevated host.'
    }

    $underTest = $false

    $profileName = $(if ($AllUsers) { 'AllUsers' } else { 'CurrentUser' }) `
                 + $(if ($AllHosts) { 'AllHosts' } else { 'CurrentHost' })
    Write-Verbose "`$profileName = '$profileName'"

    $profilePath = $PROFILE.$profileName
    Write-Verbose "`$profilePath = '$profilePath'"

    # Under test, we override some variables using $args as a backdoor.
    if (($TestParams.Count -gt 0) -and ($TestParams[0] -is [string])) {
        $profilePath = [string]$TestParams[0]
        $underTest = $true
        if ($TestParams.Count -gt 1) {
            $ModuleBasePath = [string]$TestParams[1]
        }
    }

    if (!$profilePath) { $profilePath = $PROFILE }

    if (!$Force) {
        # Search the user's profiles to see if any are using posh-git already, there is an extra search
        # ($profilePath) taking place to accomodate the Pester tests.
        $importedInProfile = Test-PoshGitImportedInScript $profilePath
        if (!$importedInProfile -and !$underTest) {
            $importedInProfile = Test-PoshGitImportedInScript $PROFILE
        }
        if (!$importedInProfile -and !$underTest) {
            $importedInProfile = Test-PoshGitImportedInScript $PROFILE.CurrentUserCurrentHost
        }
        if (!$importedInProfile -and !$underTest) {
            $importedInProfile = Test-PoshGitImportedInScript $PROFILE.CurrentUserAllHosts
        }
        if (!$importedInProfile -and !$underTest) {
            $importedInProfile = Test-PoshGitImportedInScript $PROFILE.AllUsersCurrentHost
        }
        if (!$importedInProfile -and !$underTest) {
            $importedInProfile = Test-PoshGitImportedInScript $PROFILE.AllUsersAllHosts
        }

        if ($importedInProfile) {
            Write-Warning "Skipping add of posh-git import to file '$profilePath'."
            Write-Warning "posh-git appears to already be imported in one of your profile scripts."
            Write-Warning "If you want to force the add, use the -Force parameter."
            return
        }
    }

    if (!$profilePath) {
        Write-Warning "Skipping add of posh-git import to profile; no profile found."
        Write-Verbose "`$PROFILE              = '$PROFILE'"
        Write-Verbose "CurrentUserCurrentHost = '$($PROFILE.CurrentUserCurrentHost)'"
        Write-Verbose "CurrentUserAllHosts    = '$($PROFILE.CurrentUserAllHosts)'"
        Write-Verbose "AllUsersCurrentHost    = '$($PROFILE.AllUsersCurrentHost)'"
        Write-Verbose "AllUsersAllHosts       = '$($PROFILE.AllUsersAllHosts)'"
        return
    }

    # If the profile script exists and is signed, then we should not modify it
    if (Test-Path -LiteralPath $profilePath) {
        if (!(Get-Command Get-AuthenticodeSignature -ErrorAction SilentlyContinue))
        {
            Write-Verbose "Platform doesn't support script signing, skipping test for signed profile."
        }
        else {
            $sig = Get-AuthenticodeSignature $profilePath
            if ($null -ne $sig.SignerCertificate) {
                Write-Warning "Skipping add of posh-git import to profile; '$profilePath' appears to be signed."
                Write-Warning "Add the command 'Import-Module posh-git' to your profile and resign it."
                return
            }
        }
    }

    # Check if the location of this module file is in the PSModulePath
    if (Test-InPSModulePath $ModuleBasePath) {
        $profileContent = "`nImport-Module posh-git"
    }
    else {
        $modulePath = Join-Path $ModuleBasePath posh-git.psd1
        $profileContent = "`nImport-Module '$modulePath'"
    }

    # Make sure the PowerShell profile directory exists
    $profileDir = Split-Path $profilePath -Parent
    if (!(Test-Path -LiteralPath $profileDir)) {
        if ($PSCmdlet.ShouldProcess($profileDir, "Create current user PowerShell profile directory")) {
            New-Item $profileDir -ItemType Directory -Force -Verbose:$VerbosePreference > $null
        }
    }

    if ($PSCmdlet.ShouldProcess($profilePath, "Add 'Import-Module posh-git' to profile")) {
        Add-Content -LiteralPath $profilePath -Value $profileContent -Encoding UTF8
    }
}