Why does Powershell replace commas with whitespaces? - string

Question

I'm doing some script in Powershell to automate a task. This script is going to get arguments, such as:
PS > myscript.ps1 par=a,1,2,0.1 par=b,3,4,0.1 par=c,5,6,0.1 bin=file.exe exeargs="fixed args for file.exe"
In short, file.exe is an executable which accept parameters (including a, b and c) and this ps1 script is going to execute file.exe passing args a, b and c within the specified range, varying 'em by the specified precision.
The question is, I first split each $arg in $args by the character "=", and then I should split them by "," to get the specified values.
The thing is, when I do:
foreach ($arg in $args)
{
$parts = ([string] $arg).split("=")
Write-Host $parts[1]
}
The output is
a 1 2 0.1
b 3 4 0.1
c 5 6 0.1
file.exe
fixed args for file.exe
I.e., it already substituted the "," character with a whitespace, so my second split should be with white space, not with comma.
Any guess on why does it happen?
Thanks in advance!

Answer 1

First of all why are you writing it like a C program or something? You don't have to pass arguments like that, use $args and split on = etc. when Powershell has a more powerful concept of parameters, whereby you can pass the named paramters and arguments rather than doing the parsing that you are doing. ( More on parameters here: http://technet.microsoft.com/en-us/library/dd315296.aspx)
With that said, let me answer your question:
What you are doing is when you pass in arguments like:
par=a,1,2,0.1 par=b,3,4,0.1 par=c,5,6,0.1 bin=file.exe exeargs="fixed args for file.exe"
you are passing in array of arrays. The first element is the array with elements:
par=a
1
2
0.1
Ok coming to the split:
When you do [string] $a, you are converting the array into a string. By default this means an array with elements 1,2,3 will become 1 2 3.
So your first argument there par=a,1,2,0.1, becomes par=a 1 2 0.1 and the split on = means parts[1] becomes a 1 2 0.1, which is what you see.
So how can you retain the comma?
Just make an array to be converted into a string with , inbetween than space, right?
Here are some ways to do that:
Using -join operator:
foreach ($arg in $args)
{
$parts = ($arg -join ",").split("=")
Write-Host $parts[1]
}
now you will see the output with the commas that you want.
Another way, using $ofs special variable:
foreach ($arg in $args)
{
$ofs =","
$parts = ([string] $arg).split("=")
Write-Host $parts[1]
}
(more on $ofs here: http://blogs.msdn.com/b/powershell/archive/2006/07/15/what-is-ofs.aspx )
Disclaimer - All this explanation to make you understand what is happening. Please do not continue this and use paramters.

Answer 2

This is happening in the parsing of the command line for your script and not during the split() method. To see this, try putting a "Write-Host $args" at the beginning, like so:
Write-Host $args
foreach ($arg in $args)
{
$parts = ([string] $arg).split("=")
Write-Host $parts[1]
}
This is because the ',' character is used to separate elements in an array. For example:
PS C:\temp> $a = 1,2,3
PS C:\temp> Write-Host $a
1 2 3
PS C:\temp> $a.GetType()
IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True Object[] System.Array
Try this command line instead:
.\myscript.ps1 "par=a,1,2,0.1" "par=b,3,4,0.1" "par=c,5,6,0.1" "bin=file.exe" "exeargs=fixed args for file.exe"