Problems calling shell command from .net core Linux - linux

Question

I have some problems calling commands from a Linux .net core consol application.
Sub Main()
Dim PI As New ProcessStartInfo
Using Proc As New Process
With PI
.FileName = "cat"
.Arguments = "/etc/*-release"
.RedirectStandardOutput = True
.UseShellExecute = False
.CreateNoWindow = True
End With
Proc.StartInfo = PI
Proc.Start()
PI = Nothing
Console.Write(Proc.StandardOutput.ReadToEnd)
End Using
End Sub
I get this error:
cat: '/etc/*-release': No such file or directory
It work if I disable redirection and set UseShellExecute = True, but I would like to be able to use the output in my code.

Answer 1

When you run a command like
cat /etc/*-release
The linux shell (bash, probably) evaluates each argument, then calls the program with the evaluated arguments. Simple words evaluate to themselves, but variables (like $SOME_ARGUMENT) and patterns (like *) evaluate to the values and file names. So the shell really evaluates the above into (assuming there is just one file):
cat /etc/os-release
And so the cat program just gets that one argument - without any globs like *.
If you want to emulate that behaviour in your program, you need to set UseShellExecute to True.
Or, perhaps you can do the evaluation yourself. APIs like Directory.EnumerateFiles let you do that:
Dim textFiles = Directory.EnumerateFiles("/etc/", "*-release")
Then you need to walk this collection and use the exact file name as your .Arguments value.
Edit: But to go a bit further, why are you even trying to do this? If you have read the file completely, why call cat. Why not just Console.WriteLine() the file itself rather than calling cat?

Answer 2

Ahhh....got it!
I just have to use bash -c ""cat ""/etc/*-release""""
Sub Main()
Dim PI As New ProcessStartInfo
Using Proc As New Process
With PI
.FileName = "bash"
.Arguments = "-c ""cat ""/etc/*-release"""""
.RedirectStandardOutput = True
.UseShellExecute = False
.CreateNoWindow = True
End With
Proc.StartInfo = PI
Proc.Start()
PI = Nothing
Console.Write(Proc.StandardOutput.ReadToEnd)
End Using
End Sub