17

For whatever reason, when I try to call a C# program I'm writing, and I try to pass two arguments with '--' in the command line, PowerShell doesn't call the program with my command line.

For instance, I'm providing the command line:

.\abc.exe foo.txt -- bar --

When I call this, the C# program's main only gets the command line arguments:

foo.txt bar --

instead of

foo.txt -- bar --

as would be expected.

Why would this be happening?

BTW, if I call it as:

.\abc.exe foo.txt '--' bar '--'

it works as expected.

Also, calling it as:

& .\abc.exe foo.txt -- bar --

Doesn't seem to help.

My reason for thinking this is a PowerShell weirdness is that if I run the same command line from CMD.EXE, everything works as expected.

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1
  • a further note. apparently the two '--' isn't the whole problem. It seems that powershell dropbx the first '--' even if the second one isn't there. Seems like -- must have special meaning for powershell. Commented Apr 3, 2013 at 6:27

2 Answers 2

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17

A double hyphen instructs PowerShell to treat everything coming after as literal arguments rather than options, so that you can pass for instance a literal -foo to your script/application/cmdlet.

Example:

PS C:\> echo "-bar" | select-string -bar Select-String : A parameter cannot be found that matches parameter name 'bar'. At line:1 char:28 + "-bar" | select-string -bar <<<< + CategoryInfo : InvalidArgument: (:) [Select-String], ParameterBindingException + FullyQualifiedErrorId : NamedParameterNotFound,Microsoft.PowerShell.Commands.SelectStringCommand

vs.

PS C:\> echo "-bar" | select-string -- -bar -bar

To avoid this behavior you must either quote ("--", '--') or escape (`--) the double hyphen.

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5 Comments

Can you give a reference to doc somewhere that describes the purpose of '--' and how it instructs PS to do this?
This answer from @ravikanth to a similar question cites "Windows PowerShell in Action", but other than that I don't have a source. It's consistent with other shells, though (bash for instance).
Here's a source for running executables in PowerShell that's well worth looking at: social.technet.microsoft.com/wiki/contents/articles/…
@JamieSee I don't see the double-dash discussed in that article, only the "stop parsing" parameter (--%) that was introduced with PowerShell v3.
I anyone is looking for the official docs about this -- feature, here it is.
10

With PowerShell 3 you can use --% to stop the normal parsing PowerShell does.

.\abc.exe --% foo.txt -- bar --
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