Fix removing all lines from crontab

demos/crontab.ps1

@@ -1,9 +1,26 @@
-# Use the crontab module available at ./modules/CronTab
+
+if (!($env:PSMODULEPATH -split ';' | Where-Object { $_.StartsWith($PSScriptRoot) }))
+{
+    $env:PSMODULEPATH += ";$PSScriptRoot/modules"
+}
+
+Import-Module CronTab
 
 # Get the existing cron jobs
+Get-CronJob
+
+# New cron job to clean out tmp every day at 1am
+New-CronJob -Command 'rm -rf /tmp/*' -Hour 1
+
+# New cron job to start a build
+New-CronJob -Command 'powershell -c "cd ~/src/PowerShell; ipmo ./build.psm1; Start-PSBuild"' -Hour 2 -DayOfWeek 1-5
 
 # Sort them by data
-
-# Create a new one using a DateTime object
+Get-CronJob | Sort-Object Command
 
 # Show in bash that the new cron job exists
+crontab -l
+
+# Remove a cron job
+Get-CronJob | Where-Object { $_.Command -match '^powershell.*' } | Remove-CronJob
+

demos/modules/CronTab/CronTab.psm1

@@ -1,3 +1,6 @@
+
+using namespace System.Collections.Generic
+
 $crontabcmd = "/usr/bin/crontab"
 
 class CronJob {
@@ -15,7 +18,7 @@ function Get-CronTab ([String] $user) {
     $crontab = Invoke-CronTab -user $user -arguments "-l" -noThrow
     if ($crontab -is [System.Management.Automation.ErrorRecord]) {
         if ($crontab.Exception.Message.StartsWith("no crontab for ")) {
-            $crontab = $null
+            $crontab = @()
         }
         else {
             throw $crontab.Exception
@@ -85,7 +88,7 @@ function Remove-CronJob {
     process {
 
         [string[]] $crontab = Get-CronTab -user $UserName
-        [string[]] $newcrontab = $null
+        $newcrontab = [List[string]]::new()
         $found = $false
         
         foreach ($line in $crontab) {
@@ -93,7 +96,7 @@ function Remove-CronJob {
             if ((Compare-object $cronjob.psobject.properties $Job.psobject.properties) -eq $null) {
                 $found = $true
             } else {
-                $newcrontab += $line
+                $newcrontab.Add($line)
             }
         }