I have the following code:
$project.PropertyGroup | Foreach-Object {
if($_.GetAttribute('Condition').Trim() -eq $propertyGroupConditionName.Trim()) {
$a = $project.RemoveChild($_);
Write-Host $_.GetAttribute('Condition')"has been removed.";
}
};
Question #1: How do I exit from ForEach-Object? I tried using "break" and "continue", but it doesn't work.
Question #2: I found that I can alter the list within a foreach loop... We can't do it like that in C#... Why does PowerShell allow us to do that?
First of all, Foreach-Object is not an actual loop and calling break in it will cancel the whole script rather than skipping to the statement after it.
Conversely, break and continue will work as you expect in an actual foreach loop.
Item #1. Putting a break within the foreach loop does exit the loop, but it does not stop the pipeline. It sounds like you want something like this:
$todo=$project.PropertyGroup
foreach ($thing in $todo){
if ($thing -eq 'some_condition'){
break
}
}
Item #2. PowerShell lets you modify an array within a foreach loop over that array, but those changes do not take effect until you exit the loop. Try running the code below for an example.
$a=1,2,3
foreach ($value in $a){
Write-Host $value
}
Write-Host $a
I can't comment on why the authors of PowerShell allowed this, but most other scripting languages (Perl, Python and shell) allow similar constructs.
There are differences between foreach and foreach-object.
A very good description you can find here: MS-ScriptingGuy
For testing in PS, here you have scripts to show the difference.
ForEach-Object:
# Omit 5.
1..10 | ForEach-Object {
if ($_ -eq 5) {return}
# if ($_ -ge 5) {return} # Omit from 5.
Write-Host $_
}
write-host "after1"
# Cancels whole script at 15, "after2" not printed.
11..20 | ForEach-Object {
if ($_ -eq 15) {continue}
Write-Host $_
}
write-host "after2"
# Cancels whole script at 25, "after3" not printed.
21..30 | ForEach-Object {
if ($_ -eq 25) {break}
Write-Host $_
}
write-host "after3"
foreach
# Ends foreach at 5.
foreach ($number1 in (1..10)) {
if ($number1 -eq 5) {break}
Write-Host "$number1"
}
write-host "after1"
# Omit 15.
foreach ($number2 in (11..20)) {
if ($number2 -eq 15) {continue}
Write-Host "$number2"
}
write-host "after2"
# Cancels whole script at 25, "after3" not printed.
foreach ($number3 in (21..30)) {
if ($number3 -eq 25) {return}
Write-Host "$number3"
}
write-host "after3"
To stop the pipeline of which ForEach-Object is part just use the statement continue inside the script block under ForEach-Object. continue behaves differently when you use it in foreach(...) {...} and in ForEach-Object {...} and this is why it's possible. If you want to carry on producing objects in the pipeline discarding some of the original objects, then the best way to do it is to filter out using Where-Object.
Since ForEach-Object is a cmdlet, break and continue will behave differently here than with the foreach keyword. Both will stop the loop but will also terminate the entire script:
break:
0..3 | foreach {
if ($_ -eq 2) { break }
$_
}
echo "Never printed"
# OUTPUT:
# 0
# 1
continue:
0..3 | foreach {
if ($_ -eq 2) { continue }
$_
}
echo "Never printed"
# OUTPUT:
# 0
# 1
So far, I have not found a "good" way to break a foreach script block without breaking the script, except "abusing" exceptions, although powershell core uses this approach:
throw:
class CustomStopUpstreamException : Exception {}
try {
0..3 | foreach {
if ($_ -eq 2) { throw [CustomStopUpstreamException]::new() }
$_
}
} catch [CustomStopUpstreamException] { }
echo "End"
# OUTPUT:
# 0
# 1
# End
The alternative (which is not always possible) would be to use the foreach keyword:
foreach:
foreach ($_ in (0..3)) {
if ($_ -eq 2) { break }
$_
}
echo "End"
# OUTPUT:
# 0
# 1
# End
If you insist on using ForEach-Object, then I would suggest adding a "break condition" like this:
$Break = $False;
1,2,3,4 | Where-Object { $Break -Eq $False } | ForEach-Object {
$Break = $_ -Eq 3;
Write-Host "Current number is $_";
}
The above code must output 1,2,3 and then skip (break before) 4. Expected output:
Current number is 1
Current number is 2
Current number is 3
Below is a suggested approach to Question #1 which I use if I wish to use the ForEach-Object cmdlet.
It does not directly answer the question because it does not EXIT the pipeline.
However, it may achieve the desired effect in Q#1.
The only drawback an amateur like myself can see is when processing large pipeline iterations.
$zStop = $false
(97..122) | Where-Object {$zStop -eq $false} | ForEach-Object {
$zNumeric = $_
$zAlpha = [char]$zNumeric
Write-Host -ForegroundColor Yellow ("{0,4} = {1}" -f ($zNumeric, $zAlpha))
if ($zAlpha -eq "m") {$zStop = $true}
}
Write-Host -ForegroundColor Green "My PSVersion = 5.1.18362.145"
I hope this is of use.
Happy New Year to all.
There is a way to break from ForEach-Object without throwing an exception. It employs a lesser-known feature of Select-Object, using the -First parameter, which actually breaks the pipeline when the specified number of pipeline items have been processed.
Simplified example:
$null = 1..5 | ForEach-Object {
# Do something...
Write-Host $_
# Evaluate "break" condition -> output $true
if( $_ -eq 2 ) { $true }
} | Select-Object -First 1 # Actually breaks the pipeline
Output:
1
2
Note that the assignment to $null is there to hide the output of $true, which is produced by the break condition. The value $true could be replaced by 42, "skip", "foobar", you name it. We just need to pipe something to Select-Object so it breaks the pipeline.
I found this question while looking for a way to have fine grained flow control to break from a specific block of code. The solution I settled on wasn't mentioned...
Using labels with the break keyword
From: about_break
A Break statement can include a label that lets you exit embedded
loops. A label can specify any loop keyword, such as Foreach, For, or
While, in a script.
Here's a simple example
:myLabel for($i = 1; $i -le 2; $i++) {
Write-Host "Iteration: $i"
break myLabel
}
Write-Host "After for loop"
# Results:
# Iteration: 1
# After for loop
And then a more complicated example that shows the results with nested labels and breaking each one.
:outerLabel for($outer = 1; $outer -le 2; $outer++) {
:innerLabel for($inner = 1; $inner -le 2; $inner++) {
Write-Host "Outer: $outer / Inner: $inner"
#break innerLabel
#break outerLabel
}
Write-Host "After Inner Loop"
}
Write-Host "After Outer Loop"
# Both breaks commented out
# Outer: 1 / Inner: 1
# Outer: 1 / Inner: 2
# After Inner Loop
# Outer: 2 / Inner: 1
# Outer: 2 / Inner: 2
# After Inner Loop
# After Outer Loop
# break innerLabel Results
# Outer: 1 / Inner: 1
# After Inner Loop
# Outer: 2 / Inner: 1
# After Inner Loop
# After Outer Loop
# break outerLabel Results
# Outer: 1 / Inner: 1
# After Outer Loop
You can also adapt it to work in other situations by wrapping blocks of code in loops that will only execute once.
:myLabel do {
1..2 | % {
Write-Host "Iteration: $_"
break myLabel
}
} while ($false)
Write-Host "After do while loop"
# Results:
# Iteration: 1
# After do while loop
You have two options to abruptly exit out of ForEach-Object pipeline in PowerShell:
Apply exit logic in Where-Object first, then pass objects to Foreach-Object, or
(where possible) convert Foreach-Object into a standard Foreach looping construct.
Let's see examples: Following scripts exit out of Foreach-Object loop after 2nd iteration (i.e. pipeline iterates only 2 times)":
Solution-1: use Where-Object filter BEFORE Foreach-Object:
[boolean]$exit = $false;
1..10 | Where-Object {$exit -eq $false} | Foreach-Object {
if($_ -eq 2) {$exit = $true} #OR $exit = ($_ -eq 2);
$_;
}
OR
1..10 | Where-Object {$_ -le 2} | Foreach-Object {
$_;
}
Solution-2: Converted Foreach-Object into standard Foreach looping construct:
Foreach ($i in 1..10) {
if ($i -eq 3) {break;}
$i;
}
PowerShell should really provide a bit more straightforward way to exit or break out from within the body of a Foreach-Object pipeline. Note: return doesn't exit, it only skips specific iteration (similar to continue in most programming languages), here is an example of return:
Write-Host "Following will only skip one iteration (actually iterates all 10 times)";
1..10 | Foreach-Object {
if ($_ -eq 3) {return;} #skips only 3rd iteration.
$_;
}
HTH
Answer for Question #1 -
You could simply have your if statement stop being TRUE
$project.PropertyGroup | Foreach {
if(($_.GetAttribute('Condition').Trim() -eq $propertyGroupConditionName.Trim()) -and !$FinishLoop) {
$a = $project.RemoveChild($_);
Write-Host $_.GetAttribute('Condition')"has been removed.";
$FinishLoop = $true
}
};
I am taking a scripting class as part of my IT degree and I am stumped on my powershell script. I have to use Get-Date to time how long my game is played, and also create a log file that stores number of games played, and the shorted and longest games played. The log file must be created outside the script, but must update within the script. I put the code I have so far below.
$rand = new-object system.random
$number= $rand.next(0,11)
clear-host
do{ $a = read-host -prompt "enter number between 1 and 10"
if ($a -gt $Number) {Write-Host "number is too high"}
elseif ($a -lt $Number) {Write-Host "number is too low"}
elseif ($a -eq $Number) {Write-Host "You did it!! It took you $x tries!"}
else {"You have to guess a number!!!"}
$x = $x + 1
} while ($a -ne $number)
$path = C:\temp\logfile.log.txt
To time execution, grab the date before and after you've done your work, and then subtract the two to get a TimeSpan representing the time it took
$StartTime = Get-Date
# script goes here
$EndTime = Get-Date
$TimeTaken = $EndTime - $StartTime
Write-Host "A total of $($TimeTaken.TotalSeconds) has passed"
You could also use the StopWatch class to accomplish this:
$Watch = [System.Diagnostics.Stopwatch]::StartNew()
# script goes here
$Watch.Stop()
$TimeTaken = $Watch.Elapsed
Write-Host "A total of $($TimeTaken.TotalSeconds) has passed"
Why won't this work?
if (([datetime] $a = Date),$a.DayOfWeek -ne 'Wednesday'){
Write-Host 1
Exit
}ElseIf ($a.hour -ne 9){
Write-Host 2
Exit
}
Do stuff...
but this will
if (($connected = Test-Connection 1.1.1.1 -Quiet), $connected -eq $false){
Start-Process msg -ArgumentList "$env:USERNAME Not Connected..."
Exit
}
Do stuff..
In the first example my script always exits unless I move [datetime] $a = date outside if statement. However, the second example works without issue.
Also, if insert $a in the first if statement it returns the correct datetime.
Don't use , inside an if statement, as it results in the creation of a 2-item array - an object that if() will always evaluate to $true.
The reason for this, is that when you enclose an assignment operation in plaint parentheses (that is: (), not $() which a the subexpression operator), the right-hand side of the assignment is itself returned:
PS C:\> $null = 123 # the operation itself doesn't generate output
PS C:\> ($null = 123) # but we can force it to do so
123
So when you do something like:
($a = Get-Date),$a -eq (Get-Date)
you're really producing the following expression: #($a,$a) -eq (Get-Date)
You can do it like this instead:
if(([datetime]$a = Date).DayOfWeek -ne 'Wednesday'){
# It's not wednesday
}
and
if (($connected = Test-Connection 1.1.1.1 -Quiet) -eq $false){
# No response
}
I ultimately used the following code:
if ($([datetime] $a = Date; $a.DayOfWeek -ne 'Wednesday') -eq $true){
Write-Host 1
Exit
}ElseIf ($a.hour -ne 9){
Write-Host 2
Exit
}
Do stuff..
and
if ($($connected = Test-Connection 1.1.1.1 -Quiet; $connected) -eq $false){
Write-Host 3
Exit
}
Do stuff..
I have a script that pings an ip address and send that information to a console window. In the case of high ping times or missed pings, it is also written to a log. I would like to keep only the high ping times and missed pings in the console window and allow the good pings to overwrite each other. Is that possible?
For high ping times, this is the output (similar code is used for missed pings).
$out = ("{0}ms at $(get-date -format G)" -f $ping.ResponseTime)
write-host $out -foregroundcolor "yellow"
$out >> .\runningPing$ipAddress.txt
For normal ping times, the output is this.
$out ("{0}ms" -f $ping.ResponseTime)
write-host $out -foregroundcolor "green"
I'd like to make that last line just overwrite itself for normal pings, but let the high and missed pings push up the screen as the program runs. Is that something I can do in PS?
SOLUTION
Thanks to #Mathias R. Jensen, I came up with this solution:
if ($ping.statuscode -eq 0) {
if ($ping.responsetime -gt $waitTime) {
$highPings = $highPings + 1
$out = ("{0}ms at $(get-date -format G)" -f $ping.ResponseTime)
[console]::SetCursorPosition(0,$highPings + $droppedPings + 1)
write-host $out -foregroundcolor "yellow"
$out >> $outFile
}
else {
$out = ("{0}ms $i of $pingCount" -f $ping.ResponseTime)
[console]::SetCursorPosition(0,$highPings + $droppedPings + 2)
write-host $out -foregroundcolor "green"
}
}
else {
$droppedPings = $droppedPings + 1
$out = ("missed ping at $(get-date -format G)")
[console]::SetCursorPosition(0,$highPings + $droppedPings + 1)
write-host $out -foregroundcolor "red"
$out >> $outFile
}
I think you should use Write-Progress for the good pings. You don't need to give a percentage, and you can use the -Status parameter to show just the last good one.
Here's a small example I wrote that might demonstrate how it would look/operate (you can execute this yourself to see, it doesn't ping anything it's just a simulation):
$goods = 0
0..100 | % {
if ((Get-Random -Minimum 0 -Maximum 100) -ge 50) {
$goods += 1
Write-Progress -Activity Test -Status "Last good ping: $_ ($goods total good pings)"
} else {
Write-Warning "Bad ping"
}
Start-Sleep -Seconds 1
}
In this case you could have even calculated, for example a percentage of good pings and used that in Write-Progress but I wanted to show that you don't need to use it as a progress bar for it to be useful.
As I mentioned in the comments, the cursor position can be controlled by this method:
[control]::SetCursorPosition([int]$x,[int]$y)
The [console] type accelerator points to the same Console class that enables you to WriteLine() to the console in a C# console application. You can also control colors and other console behavior if you feel like it:
Clear-Host
[console]::ForegroundColor = "Red"
1..10|%{
[console]::SetCursorPosition(2+$_,$_-1)
[console]::WriteLine("Hello World!")
}
[console]::ForegroundColor = "Green"
briantist has the better approach to this but I was playing around and came up with this as well. It will not work in ISE but should do it's job on the PowerShell console. It uses "`b" which is the backspace character so that the text will overwrite itself on the console host write. Might not help you but could be useful to others.
switch($ping.ResponseTime){
{$_ -ge 0 -and $_ -le 100}{
$out = "{0}ms" -f $_
$options = #{ForegroundColor = "Green"; NoNewline = $true}
$backup = "`b" * $out.Length
}
{$_ -ge 500 -and $_ -le 900}{
$out = "{0}ms at $(get-date -format G)" -f $_
$options = #{ForegroundColor = "Yellow"; NoNewline = $false}
$backup = "`n"
}
}
Write-Host "$backup$out" #options
Uses a switch to set the options based on the the range of ping times. Sets a small hash table which is splatted to the write-host. Not perfect but it shows another way to do it.
Again this mostly done for fun.
I have tried below but not getting any result back
Not sure if i'm doing this well.
Can i filter in the foreach or in my if statement
Thanks in advance
[DateTime] $CreatedDate = $item["Created"]
$convertedCreatedDate = $CreatedDate.ToString("yyyy-MM-dd")
$today = (Get-Date).AddDays(-1).ToString("yyyy-MM-dd")
foreach ($item in $list.items | where {$convertedCreatedDate -eq $today}) {
if ($list.items | where {$convertedCreatedDate -eq $today})
{
Write-Host $item["Created"]
}
Write-Host $item["Created"]
}
You can use a complex expression in your foreach as you're doing above. I would wrap it in a #() to make the code a bit more readable and to ensure the result is an array (either length 0, 1 or n) e.g.:
foreach ($item in #($list.items | where {$convertedCreatedDate -eq $today})) {
You can also simplify you're date testing by using the Date property on a DateTime e.g.:
$convertedCreatedDate = ([DateTime]$item["Created"]).Date
$today = (Get-Date).Date
You can also put a complex expression within an if statement condition but PowerShell will only evaluate whether the statement is $true or $false. PowerShell does lots of coercion to try to take something like:
$list.items | where {$convertedCreatedDate -eq $today}
And convert that to a boolean. Essentially if the pipeline evaluates to a non-empty result, the result is $true otherwise it is $false. This is probably not what you intended.
Try this:
$today=(Get-Date).AddDays(-1).ToString("yyyy-MM-dd")
foreach ($item in $list.items) {
[DateTime]$CreatedDate=$item["Created"]
$convertedCreatedDate=$CreatedDate.ToString("yyyy-MM-dd")
if ($convertedCreatedDate -eq $today) {
Write-Host $item["Created"]
}
}