What does the $ symbol mean? I saw it in this script:
function sendColor($colorName)
{
$portInfo = ( Get-WmiObject Win32_SerialPort | Where { $_.PNPDeviceID -like '*VID_239A*' } | select -last 1 )
$port = new-Object System.IO.Ports.SerialPort $portInfo.DeviceID,9600,None,8,one
$port.open()
$text = $colorName + "`r"
$port.Write($text)
start-sleep -m 50
$port.ReadExisting()
$port.Close()
}
if ($args.Length -eq 0)
{
echo "Usage: ColorChange <color>"
}
else
{
sendColor($args[0])
}
As far as I know this is a PowerShell script, but I'm not sure.
Taken from the documentation in:
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_variables?view=powershell-7
"A variable is a unit of memory in which values are stored. In PowerShell, variables are represented by text strings that begin with a dollar sign ($), such as $a, $process, or $my_var."
i want to run some conditional looping code along with other task like running a .bat file in one .ps1 file. I dont have sound knowledge in poweershell but i am trying to do this.
i tried to run the file but only batch file is executing successfully but not the code that needs to perform a different tasks in the process.
i tried using this command to run .batch file
cmd.exe /k ""c:\Users\ADM_SPANCHADULA\Desktop\status_check\status.bat" & powershell"
which is executing fine. but the remaining part
cd C:\Users\ADM_SPANCHADULA\Desktop\status_check
cmd.exe /c "c:\Users\ADM_SPANCHADULA\Desktop\status_check\status.bat"
"hello world " | Out-Host
$a=0
Do {
$output1 = Compare-Object (get-content "Job_status.txt") (get-content "done.txt")
$output2 = Compare-Object (get-content "Job_status.txt") (get-content "warn.txt")
if ( $output1 = "" ) {
$a = 1
$a|Out-Host
} elseif ( $output2 = "" ) {
$a = 1
$a|Out-Host
} else {
echo "looping "
}
} while ( $a -gt 0 )
is not executing .
can someone please help me out.
Is ther any way in Powershell to pipe in from an virable instead of a file?
There are commands that I need to pipe into another command, right now that is done by first creating a file with the additional commands, and then piping that file into the original command. Code looks somehting like this now:
$val = "*some command*" + "`r`n" + "*some command*" + "`r`n" + "*some command*"
New-Item -name Commands.txt -type "file" -value $val
$command = #'
db2cmd.exe /C '*custom db2 command* < \Commands.txt > \Output.xml'
'#
Invoke-Expression -Command:$command
So instead of creating that file, can I somehow just pipe in $val insatead of Commands.txt?
Try this
$val = #("*some command*1","*some command2*","*some command3*")
$val | % { db2cmd.exe /C $_ > \Output.xml }
You should be able to pipe in from $val provided you use Write-Output or its shorthand echo, but it may also be worth trying passing the commands directly on the command line. Try this (and if it doesn't work I can delete the answer):
PS C:\> filter db2cmd() { $_ | db2cmd.exe ($args -replace '(\\*)"','$1$1\"') }
PS C:\> $val = #"
>> *custom db2 command*
>> *some command*
>> *some command*
>> *some command*
>> "#
>>
PS C:\> db2cmd /C $val > \Output.xml
What happens here is that Windows executables receive their command line from a single string. If you run them from cmd.exe you cannot pass newlines in the argument string, but Powershell doesn't have that restriction so with many programs you can actually pass multiple lines as a single argument. I don't know db2cmd.exe so it might not work here.
The strange bit of string replacement is to handle any double quotes in the arguments: Powershell doesn't quote them and the quoting rules expected by most exe files are a bit bizarre.
The only limitation here would be that $val must not exceed about 32,600 characters and cannot contain nulls. Any other restrictions (such as whether non-ascii unicode characters work) would depend on the application.
Failing that:
echo $val | db2cmd.exe /C '*custom db2 command*' > \Output.xml
may work, or you can use it in combination with the filter I defined at the top:
echo $val | db2cmd /C '*custom db2 command*' > \Output.xml
I can't figure out why the following code fails:
# test.ps1
"`$args: ($args)"
"`$args count: $($args.length)"
# this fails
0..$($args.length - 1) | %{ $args[$_] = ($args[$_] -replace '`n',"`n") }
# this works
$i = 0
foreach ( $el in $args ) { $args[$i] = $args[$i] -replace '`n',"`n"; $i++ }
"$args"
I'm calling it like so:
rem from cmd.exe
powershell.exe -noprofile -file test.ps1 "a`nb" "c"
Scoping issue. The $args inside the foreach-object (%) scriptblock is local to that scriptblock. The following works:
"`$args: $args"
"`$args count: $($args.length)"
$a = $args
# this fails
0..$($args.length - 1) | %{ $a[$_] = ($a[$_] -replace '`n',"`n") }
$a
Keith answered this question. Just wanted to add some more info, because I found it useful many times. Look at the code:
[21]: function test{
>> $args -replace '`n',"`n"
>> }
>>
[22]: test 'replace all`nnew' 'lines`nin the `nstring' 'eof`ntest'
replace all
new
lines
in the
string
eof
test
The -replace operator works with array too!
Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 3 years ago.
Improve this question
A while back I was reading about multi-variable assignments in PowerShell. This lets you do things like this
64 > $a,$b,$c,$d = "A four word string".split()
65 > $a
A
66 > $b
four
Or you can swap variables in a single statement
$a,$b = $b,$a
What little known nuggets of PowerShell have you come across that you think may not be as well known as they should be?
The $$ command. I often have to do repeated operations on the same file path. For instance check out a file and then open it up in VIM. The $$ feature makes this trivial
PS> tf edit some\really\long\file\path.cpp
PS> gvim $$
It's short and simple but it saves a lot of time.
By far the most powerful feature of PowerShell is its ScriptBlock support. The fact that you can so concisely pass around what are effectively anonymous methods without any type constraints are about as powerful as C++ function pointers and as easy as C# or F# lambdas.
I mean how cool is it that using ScriptBlocks you can implement a "using" statement (which PowerShell doesn't have inherently). Or, pre-v2 you could even implement try-catch-finally.
function Using([Object]$Resource,[ScriptBlock]$Script) {
try {
&$Script
}
finally {
if ($Resource -is [IDisposable]) { $Resource.Dispose() }
}
}
Using ($File = [IO.File]::CreateText("$PWD\blah.txt")) {
$File.WriteLine(...)
}
How cool is that!
A feature that I find is often overlooked is the ability to pass a file to a switch statement.
Switch will iterate through the lines and match against strings (or regular expressions with the -regex parameter), content of variables, numbers, or the line can be passed into an expression to be evaluated as $true or $false
switch -file 'C:\test.txt'
{
'sometext' {Do-Something}
$pwd {Do-SomethingElse}
42 {Write-Host "That's the answer."}
{Test-Path $_} {Do-AThirdThing}
default {'Nothing else matched'}
}
$OFS - output field separator. A handy way to specify how array elements are separated when rendered to a string:
PS> $OFS = ', '
PS> "$(1..5)"
1, 2, 3, 4, 5
PS> $OFS = ';'
PS> "$(1..5)"
1;2;3;4;5
PS> $OFS = $null # set back to default
PS> "$(1..5)"
1 2 3 4 5
Always guaranteeing you get an array result. Consider this code:
PS> $files = dir *.iMayNotExist
PS> $files.length
$files in this case may be $null, a scalar value or an array of values. $files.length isn't going to give you the number of files found for $null or for a single file. In the single file case, you will get the file's size!! Whenever I'm not sure how much data I'll get back I always enclose the command in an array subexpression like so:
PS> $files = #(dir *.iMayNotExist)
PS> $files.length # always returns number of files in array
Then $files will always be an array. It may be empty or have only a single element in it but it will be an array. This makes reasoning with the result much simpler.
Array covariance support:
PS> $arr = '127.0.0.1','192.168.1.100','192.168.1.101'
PS> $ips = [system.net.ipaddress[]]$arr
PS> $ips | ft IPAddressToString, AddressFamily -auto
IPAddressToString AddressFamily
----------------- -------------
127.0.0.1 InterNetwork
192.168.1.100 InterNetwork
192.168.1.101 InterNetwork
Comparing arrays using Compare-Object:
PS> $preamble = [System.Text.Encoding]::UTF8.GetPreamble()
PS> $preamble | foreach {"0x{0:X2}" -f $_}
0xEF
0xBB
0xBF
PS> $fileHeader = Get-Content Utf8File.txt -Enc byte -Total 3
PS> $fileheader | foreach {"0x{0:X2}" -f $_}
0xEF
0xBB
0xBF
PS> #(Compare-Object $preamble $fileHeader -sync 0).Length -eq 0
True
Fore more stuff like this, check out my free eBook - Effective PowerShell.
Along the lines of multi-variable assignments.
$list = 1,2,3,4
While($list) {
$head, $list = $list
$head
}
1
2
3
4
I've been using this:
if (!$?) { # if previous command was not successful
Do some stuff
}
and I also use $_ (current pipeline object) quite a bit, but these might be more known than other stuff.
The fact that many operators work on arrays as well and return the elements where a comparison is true or operate on each element of the array independently:
1..1000 -lt 800 -gt 400 -like "?[5-9]0" -replace 0 -as "int[]" -as "char[]" -notmatch "\d"
This is faster than Where-Object.
Not a language feature but super helpful
f8 -- Takes the text you have put in already and searches for a command that starts with that text.
Tab-search through your history with #
Example:
PS> Get-Process explorer
PS> "Ford Explorer"
PS> "Magellan" | Add-Content "great explorers.txt"
PS> type "great explorers.txt"
PS> #expl <-- Hit the <tab> key to cycle through history entries that have the term "expl"
Love this thread. I could list a ton of things after reading Windows Powershell in Action. There's a disconnect between that book and the documentation. I actually tried to list them all somewhere else here, but got put on hold for "not being a question".
I'll start with foreach with three script blocks (begin/process/end):
Get-ChildItem | ForEach-Object {$sum=0} {$sum++} {$sum}
Speaking of swapping two variables, here's swapping two files:
${c:file1.txt},${c:file2.txt} = ${c:file2.txt},${c:file1.txt}
Search and replace a file:
${c:file.txt} = ${c:file.txt} -replace 'oldstring','newstring'
Using assembly and using namespace statements:
using assembly System.Windows.Forms
using namespace System.Windows.Forms
[messagebox]::show('hello world')
A shorter version of foreach, with properties and methods
ps | foreach name
'hi.there' | Foreach Split .
Use $() operator outside of strings to combine two statements:
$( echo hi; echo there ) | measure
Get-content/Set-content with variables:
$a = ''
get-content variable:a | set-content -value there
Anonymous functions:
1..5 | & {process{$_ * 2}}
Give the anonymous function a name:
$function:timestwo = {process{$_ * 2}}
Anonymous function with parameters:
& {param($x,$y) $x+$y} 2 5
You can stream from foreach () with these, where normally you can't:
& { foreach ($i in 1..10) {$i; sleep 1} } | out-gridview
Run processes in background like unix '&', and then wait for them:
$a = start-process -NoNewWindow powershell {timeout 10; 'done a'} -PassThru
$b = start-process -NoNewWindow powershell {timeout 10; 'done b'} -PassThru
$c = start-process -NoNewWindow powershell {timeout 10; 'done c'} -PassThru
$a,$b,$c | wait-process
Or foreach -parallel in workflows:
workflow work {
foreach -parallel ($i in 1..3) {
sleep 5
"$i done"
}
}
work
Or a workflow parallel block where you can run different things:
function sleepfor($time) { sleep $time; "sleepfor $time done"}
workflow work {
parallel {
sleepfor 3
sleepfor 2
sleepfor 1
}
'hi'
}
work
Three parallel commands in three more runspaces with the api:
$a = [PowerShell]::Create().AddScript{sleep 5;'a done'}
$b = [PowerShell]::Create().AddScript{sleep 5;'b done'}
$c = [PowerShell]::Create().AddScript{sleep 5;'c done'}
$r1,$r2,$r3 = ($a,$b,$c).begininvoke()
$a.EndInvoke($r1); $b.EndInvoke($r2); $c.EndInvoke($r3) # wait
($a,$b,$c).Streams.Error # check for errors
($a,$b,$c).dispose() # cleanup
Parallel processes with invoke-command, but you have to be at an elevated prompt with remote powershell working:
invoke-command localhost,localhost,localhost { sleep 5; 'hi' }
An assignment is an expression:
if ($a = 1) { $a }
$a = $b = 2
Get last array element with -1:
(1,2,3)[-1]
Discard output with [void]:
[void] (echo discard me)
Switch on arrays and $_ on either side:
switch(1,2,3,4,5,6) {
{$_ % 2} {"Odd $_"; continue}
4 {'FOUR'}
default {"Even $_"}
}
Get and set variables in a module:
'$script:count = 0
$script:increment = 1
function Get-Count { return $script:count += $increment }' > counter.psm1 # creating file
import-module .\counter.psm1
$m = get-module counter
& $m Get-Variable count
& $m Set-Variable count 33
See module function definition:
& $m Get-Item function:Get-Count | foreach definition
Run a command with a commandinfo object and the call operator:
$d = get-command get-date
& $d
Dynamic modules:
$m = New-Module {
function foo {"In foo x is $x"}
$x=2
Export-ModuleMember -func foo -var x
}
flags enum:
[flags()] enum bits {one = 1; two = 2; three = 4; four = 8; five = 16}
[bits]31
Little known codes for the -replace operator:
$number Substitutes the last submatch matched by group number.
${name} Substitutes the last submatch matched by a named capture of the form (?).
$$ Substitutes a single "$" literal.
$& Substitutes a copy of the entire match itself.
$` Substitutes all the text from the argument string before the matching portion.
$' Substitutes all the text of the argument string after the matching portion.
$+ Substitutes the last submatch captured.
$_ Substitutes the entire argument string.
Demo of workflows surviving interruptions using checkpoints. Kill the window or reboot. Then start PS again. Use get-job and resume-job to resume the job.
workflow test1 {
foreach ($b in 1..1000) {
$b
Checkpoint-Workflow
}
}
test1 -AsJob -JobName bootjob
Emacs edit mode. Pressing tab completion lists all the options at once. Very useful.
Set-PSReadLineOption -EditMode Emacs
Any command that begins with "get-", you can leave off the "get-":
date
help
End parsing --% and end of parameters -- operators.
write-output --% -inputobject
write-output -- -inputobject
Tab completion on wildcards:
cd \pro*iles # press tab
Compile and import a C# module with a cmdlet inside, even in Osx:
Add-Type -Path ExampleModule.cs -OutputAssembly ExampleModule.dll
Import-Module ./ExampleModule.dll
Iterate backwards over a sequence just use the len of the sequence with a 1 on the other side of the range:
foreach( x in seq.length..1) { Do-Something seq[x] }