Unable to capture plink.exe output using process.standardoutput

Question

User1284979839 posted

Hello Team, 

I am trying execute remote command on a linux machine via Asp.net (vb.net), however unable to capture the output..

I tried many diff ways like:

1. Calling directly plink.exe from asp.net and then passing the argument

2. escapsulating the plink.exe command inside a batch file and then calling that batch file from the asp.net 

The same batch file is running fine when I am calling from CMD. Below provided is the code ( any help on this is highly appreciated ).. Here I am calling the Plink.exe directly.. 

Protected Sub Button9_Click(ByVal sender As System.Object, ByVal e As EventArgs) Handles Button9.Click
Dim Srv As String
Label1.Text = ""
Dim lineCount As Integer = 0
Dim output1 As StringBuilder = New StringBuilder()

Srv = TextBox9.Text

Dim p As New Process()
p.StartInfo.FileName = "D:\plink.exe"
p.StartInfo.Arguments = " -ssh user1@someserver -pw <somepassword> -m D:\Unix_test.txt"
p.StartInfo.UseShellExecute = False
p.StartInfo.RedirectStandardOutput = True
p.StartInfo.RedirectStandardError = True
p.Start()
Dim i = 1
While i < 200
output = output & p.StandardOutput.ReadLine() & "<br>"
i = i + 1

End While


p.WaitForExit()
p.Close()

Label1.Visible = True
Label1.Text = output
End Sub

-m text file (i.e. unix_test.txt) has the below 

df -k

if I call from batch file then the batch file has the below line.. 

D:\plink -l someusername -pw somepassword <ServerName> -m D:\unix_test.txt

When I am running the same command using windows command prompt, I am getting the desired result. 

A quick help is much appreciated.. 

Answer 1

User753101303 posted

Hi,

What if you try output=p.StandardOutput.ReadToEnd() rather than this kind of hardcoded loop?

Also you tried to check the ExitCode. I would first make 100% sure it runs fine without the output redirection.

Answer 2

User-580799299 posted

Hi,

I have used logic like the following to successfully capture output from a FTP process that my web page started (in order to make sure the FTP commands did not have an error):

Dim p As New Process
Dim sw As New StringWriter
p.StartInfo.RedirectStandardInput = True
p.StartInfo.RedirectStandardOutput = True
p.StartInfo.UseShellExecute = False
p.StartInfo.FileName = "ftp"
p.StartInfo.Arguments = "-n -s:upload_cmds.txt " & cfg.FTPHostName
p.StartInfo.WorkingDirectory = fi.DirectoryName
p.Start()
Dim fw As StreamWriter = p.StandardInput
Dim fr As StreamReader = p.StandardOutput
While Not fr.EndOfStream
    sw.WriteLine("FtpPut: " & fr.ReadLine)
End While
sw.WriteLine()
sw.WriteLine("The FTP process Completed Successfully, but check the lines starting with 'FtpPut:' for any errors reported by the FTP Host.")
sw.WriteLine()
fw.Close()
fr.Close()

This does not appear significantly different than your sample, but in my case when debugging the code, the fr.EndOfStream check seems to trigger the execution of the FTP commands.

Answer 3

User1284979839 posted

Thanks a lot Dean and sorry for the delayed response.. Your code worked for me with a little tweak.. 

I decided to share the code for others to use it .. 

Protected Sub Button9_Click(ByVal sender As System.Object, ByVal e As EventArgs) Handles Button9.Click
        Dim Srv As String
        Label1.Text = ""
        Dim lineCount As Integer = 0
        Dim output1 As StringBuilder = New StringBuilder()

        Srv = TextBox9.Text

        Dim p As New Process()

        Dim sw As New StringWriter
        p.StartInfo.RedirectStandardInput = True
        p.StartInfo.RedirectStandardOutput = True
        p.StartInfo.UseShellExecute = False
        p.StartInfo.FileName = "D:\plink.exe"
        p.StartInfo.Arguments = " -ssh someusr@" & Srv & " -pw somepassword -m D:\Unix_test.txt"
        p.StartInfo.WorkingDirectory = "D:\"
        p.Start()
        Dim fw As StreamWriter = p.StandardInput
        Dim fr As StreamReader = p.StandardOutput

        While Not fr.EndOfStream
            output = output + fr.ReadLine + "<br>"
        End While
        
        Label1.Visible = True
        Label1.Text = "<br>" + output

        fw.Close()
        fr.Close()
        p.WaitForExit()
        p.Close()
        
    End Sub