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..
Related
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 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 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
}
};
This began as an effort to have all four (4) of the PowerShell profile scripts identify themselves and their location.
$MyInvocation.ScriptName was suggested for getting the script name, but I have yet to see it be anything other than an empty string. No, not $null, empty (''). This seems counter to many suggestions here on SO.
My first assumption was that $MyInvocation.ScriptName was $null, but that is not the case. To my surprise however, it is considered to be -lt 0. What is the rationale for comparing a String to an Int32?
I did find $MyInvocation.InvocationName which appears to give the script name, but not a directory path to it.
PS C:\Users\lit\Documents\PowerShell> Get-Content .\profile.ps1
Write-Host "Current User, All Hosts # $(Split-Path -Parent $MyInvocation.MyCommand.Definition)\$(Split-Path -Leaf $MyInvocation.MyCommand.Definition)"
Write-Host "`$MyInvocation.ScriptName is $MyInvocation.ScriptName"
Write-Host "`$MyInvocation.ScriptName -eq `$null results in $($MyInvocation.ScriptName -eq $null)"
Write-Host "`$($MyInvocation.ScriptName -eq 0) results in $($MyInvocation.ScriptName -eq 0)"
Write-Host "`$($MyInvocation.ScriptName -lt 0) results in $($MyInvocation.ScriptName -lt 0)"
Write-Host "`$($MyInvocation.ScriptName -eq '') results in $($MyInvocation.ScriptName -eq '')"
Try { '' -eq 0 }
Catch { Write-Host "Caught -lt 0" }
Write-Host $MyInvocation.InvocationName
PS C:\Users\lit\Documents\PowerShell> .\profile.ps1
Current User, All Hosts # C:\Users\lit\Documents\PowerShell\profile.ps1
$MyInvocation.ScriptName is System.Management.Automation.InvocationInfo.ScriptName
$MyInvocation.ScriptName -eq $null results in False
$(System.Management.Automation.InvocationInfo.ScriptName -eq 0) results in False
$(System.Management.Automation.InvocationInfo.ScriptName -lt 0) results in True
$(System.Management.Automation.InvocationInfo.ScriptName -eq '') results in True
False
.\profile.ps1
Suggestion from JosefZ works.
PS C:\src\my-powershell> type .\gname.ps1
Write-Host "`$MyInvocation.InvocationName is $((Resolve-Path $MyInvocation.InvocationName).Path)"
Write-Host (Resolve-Path $MyInvocation.InvocationName).Path
PS C:\src\my-powershell> .\gname.ps1
$MyInvocation.InvocationName is C:\src\my-powershell\gname.ps1
C:\src\my-powershell\gname.ps1
I have tried to collect these possible answers, but still only one or two deliver what is needed. $MyInvocation.Command is always $null and $MyInvocation.ScriptName is always and empty string ('').
PS C:\src\t> Get-Content callme.ps1
"=== These two give the full path and invocation path"
Write-Host "$(Split-Path -Parent $MyInvocation.MyCommand.Definition)\$(Split-Path -Leaf $MyInvocation.MyCommand.Definition)"
Write-Host "`$(`$MyInvocation.InvocationName) is $($MyInvocation.InvocationName)"
"=== `$MyInvocation.Command is `$null, but it, and its Source member, do have a type"
Write-Host "`$MyInvocation.Command -eq `$null is $($MyInvocation.Command -eq $null)"
Write-Host "`$MyInvocation.Command is $MyInvocation.Command"
Write-Host "`$(`$MyInvocation.Command) is $($MyInvocation.Command)"
Write-Host "`$MyInvocation.Command.Source is $MyInvocation.Command.Source"
Write-Host "`$(`$MyInvocation.Command.Source) is $($MyInvocation.Command.Source)"
"==="
Write-Host "`$MyInvocation.ScriptName -eq `$null is $($MyInvocation.ScriptName -eq $null)"
Write-Host "`$MyInvocation.ScriptName -eq '' is $($MyInvocation.ScriptName -eq '')"
Write-Host "`$MyInvocation.ScriptName is $MyInvocation.ScriptName"
Write-Host "`$(`$MyInvocation.ScriptName) is $($MyInvocation.ScriptName)"
PS C:\src\t> .\callme.ps1
=== These two give the full path and invocation path
C:\src\t\callme.ps1
$($MyInvocation.InvocationName) is .\callme.ps1
=== $MyInvocation.Command is $null, but it, and its Source member, do have a type
$MyInvocation.Command -eq $null is True
$MyInvocation.Command is System.Management.Automation.InvocationInfo.Command
$($MyInvocation.Command) is
$MyInvocation.Command.Source is System.Management.Automation.InvocationInfo.Command.Source
$($MyInvocation.Command.Source) is
===
$MyInvocation.ScriptName -eq $null is False
$MyInvocation.ScriptName -eq '' is True
$MyInvocation.ScriptName is System.Management.Automation.InvocationInfo.ScriptName
$($MyInvocation.ScriptName) is
Firstly, you have a bug on line 2 of your script. You probably want to wrap $MyInvocation.ScriptName in $(...):
Write-Host "`$MyInvocation.ScriptName is $($MyInvocation.ScriptName)"
Next, the try{}catch{} will only work if the expression in the try{} block throws an exception. A simple comparison doesn't do that. If you were expecting PowerShell to complain that you are comparing try different types then... it doesn't. See below.
The comment from #PetSerAl is pertinent. When you run the profile from the PowerShell prompt, the ScriptName is what calls the current command. If you were to call your profile script from another script, you'd see the calling script name. I think you might want to look at the $MyInvocation.MyCommand property instead, as per Matthias' suggestion.
And finally...
When you compare a string with a number in the way you are doing, PowerShell "protects" you and automatically treats the second entity (the number) as a string and you're left with a string comparison: is the empty string "" less than the string "0"? Why, yes it is. It is also less than "-9999":
[PS]> "" -lt -9999
True
So -9999 is bigger than nothing? Lets switch them around to check, and we see the same principle at work:
[PS]> -9999 -gt ""
False
Seemingly a contradiction unless you remember that in each case the element on the right-hand-side of the comparison is being treated as a string or int depending on what the left-hand-side is.
OK, i am trying to get this script to work and not continuously hit the same computers over and over and am having trouble getting it working. I don't think this is the best way to do it and if you have any suggestions please and thank you. Anyways there seems to be an issue with line 6 "IF (!$Succssful.Contains($Computer)) {" it doesn't shoot an error at me but instead ends the script per-maturealy. I have tried removing the "!" but no luck as I expected.
$Computers = "TrinityTechCorp"
$HotFixes = Get-Content HotFixes.csv
While ($Successful -AND $Successful.count -ne $Computers.count) {
ForEach ($Computer in $Computers) {
IF (!$Succssful.Contains($Computer)) {
If (Test-Connection $Computer) {
$Comparison = get-hotfix -ComputerName $Computer | Select -expand HotFixID
ForEach ($HotFix in $HotFixes) {
IF ($Comparison -NotLike "*$HotFix*") {
Write-Host "$Computer missing $HotFix"
}
$Successful += $Computer
}
}
}
}
}
This line
While ($Successful -AND $Successful.count -ne $Computers.count) {
can never evaluate to $true. The .count-property of a non-existing variable ($Successful) is $null, and the same goes for a string (because you specify only 1 computer, it's not an array).
To force Powershell to return the "true" number of items, use #($Successful).count and #($Computers).count instead. This will give you 1, even if $Computers wasn't defined as an array. So, with variables substituted, your line is interpreted as
While ($null -AND $null.count -ne $null) {
In Powershell 3, as you can read here, this is no longer the case.