Handling output in StartProcess RedirectedStandardOutputHandler in Cake.Build

[DmitryLukyanov]

I want to call a custom tool with cake.build via StartProcess. Let it be findstr.
All is good, StartProcess allow doing it, but now I want to analyze the searching result.
For this target I configured RedirectedStandardOutputHandler:

  settings.RedirectStandardOutput = true;
  settings.RedirectedStandardOutputHandler = (str) =>
  {
      if (str != null)
      {
         isFound = true;
      }
      return str;
  };

it works, but here some weirdness that I can't explain yet:

1. With such configuration, StartProcess returns 0 where in the rest of cases it returns 1.

2. When I call findStr in the powershell (to search some pattern in csproj), I see 2 lines in the output:

    %PATH%>findstr %Pattern% App.csproj
    <Reference Include="%Matched%">
      <HintPath>....\%Matched%.dll</HintPath>
   

but the output (str variable) in cake consist of only a single second line. The first one is missed (So there is no Reference.. line).

Can anyone bring some light on this?

[nils-a]

@DmitryLukyanov you need to share more of your code. Setting RedirectedStandardOutputHandler and/or RedirectedStandardOutput has no effect on the exit-Code or the output.

As I have written on SO (I have updated my answer), the RedirectedStandardOutputHandler will be called once for each line of output.

So, given the following script:

var target = Argument("target", "Default");
var settings = new ProcessSettings
{
 Arguments = "/I task build.cake"
};

Task("NoRedirect")
.Does(() => {
   Information("Running no redirect:");
   var exitCode = StartProcess("findstr", settings);
   Information("exited with code: " + exitCode);
});

Task("Redirect")
.Does(() => {
   Information("Running redirect:");
   settings.RedirectStandardOutput = true;
   settings.RedirectedStandardOutputHandler = (x) => {
      Information("--> " + x);
      return x;
   };
   var exitCode = StartProcess("findstr", settings);
   Information("exited with code: " + exitCode);
});

Task("Default")
   .IsDependentOn("NoRedirect")
   .IsDependentOn("Redirect");

RunTarget(target);

Cake produces the following result:

========================================
NoRedirect
========================================
Running no redirect:
Executing: "findstr" /I task build.cake
 Arguments = "/I task build.cake"
Task("NoRedirect")
Task("Redirect")
Task("Default")
exited with code: 0

========================================
Redirect
========================================
Running redirect:
Executing: "findstr" /I task build.cake
-->  Arguments = "/I task build.cake"
--> Task("NoRedirect")
--> Task("Redirect")
--> Task("Default")
-->
exited with code: 0

========================================
Default
========================================

Task                          Duration
--------------------------------------------------
NoRedirect                    00:00:00.0361745
Redirect                      00:00:00.0271926
--------------------------------------------------
Total:                        00:00:00.0646765

[DmitryLukyanov]

You can see the full code here (I see no valuable differences with the already provided). I will check your code and come back

[DmitryLukyanov]

it's my mistake. The first output log is "omitted" because it doesn't exist. I used different search patterns: with and without file extension and this is why in one case I saw 2 lines output and in another - a single line.
Regarding the error code, apparently it's related to whether a command can find anything or no. If no - the error code will be 1, otherwise - 0