[RESOLVED] cannot get error from commands in dos shell

[giodepa]

hi all,
I cannot understand why I cannot visualize error in richtextbox.text reported in dos shell.
this is my example code:

Dim start_info As New ProcessStartInfo("cmd.exe")
start_info.UseShellExecute = False
start_info.CreateNoWindow = True
start_info.RedirectStandardOutput = True
start_info.RedirectStandardError = True
 start_info.RedirectStandardInput = True
 
Dim proc As New Process()
proc.StartInfo = start_info
proc.Start()
 
proc.StandardInput.WriteLine("cd|")
proc.StandardInput.close
 
Dim std_out As StreamReader = proc.StandardOutput()
Dim std_err As StreamReader = proc.StandardError()
 
RichTextBox1.Text = std_out.ReadToEnd() + std_err.ReadToEnd()
 
 std_out.Close()
 std_err.Close()
 
proc.Close()

I should visualize in richtextbox1.text error message "the syntax of the command is incorrect" meanwhile I don't see anything.

can someone help me please?

thanks in advanced
gio

[dunfiddlin]

You can't read two streams simultaneously and concatenate them as you're trying to do here. You have to do one then the other. Unfortunately this means that your error messages will be out of order in terms of how you normally see them but it can't be avoided using this method.

[giodepa]

You can't read two streams simultaneously and concatenate them as you're trying to do here. You have to do one then the other. Unfortunately this means that your error messages will be out of order in terms of how you normally see them but it can't be avoided using this method.

I tried also using only one stream proc.StandardError without success.

[Inferrd]

Is there a reason you are using the | character in your command? Are you trying to do something else, that you haven't mentioned, that is also not producing the expected output to the RichTextBox?

I ask since changing your command to something like

proc.StandardInput.WriteLine("cdf")

will produce error text in the RichTextBox as expected.

I never got around to using DOS, so I don't have an answer as to why it's not working with "cd|". However, I believe the | character is the DOS Pipe operator. Could it be that you can't use piping while you are also redirecting standard output/error streams? As an observation, when issuing a command such as

proc.StandardInput.WriteLine("dir C:\Windows\System32 | MORE")

the | MORE seems to be ignored.


On a related note, should you want to display the output from the STDOUT and STDERR streams "simultaneously" (as opposed to any error messages all being tagged on to the very end of your RichTextBox's Text), then you could use the DOS redirect 2>&1 after your command. This would redirect STDERR to STDOUT before STDOUT is redirected to your RichTextBox. I'm sorry to say that it doesn't help with your original problem, though.

Dim start_info As New ProcessStartInfo("cmd.exe")
start_info.UseShellExecute = False
start_info.CreateNoWindow = True
start_info.RedirectStandardOutput = True
' start_info.RedirectStandardError = True
start_info.RedirectStandardInput = True
 
Dim proc As New Process()
proc.StartInfo = start_info
proc.Start()
 
proc.StandardInput.WriteLine("cdf 2>&1")
proc.StandardInput.Close()
 
Dim std_out As StreamReader = proc.StandardOutput()
'  Dim std_err As StreamReader = proc.StandardError()
 
RichTextBox1.Text = std_out.ReadToEnd() ' + std_err.ReadToEnd()
 
std_out.Close()
' std_err.Close()
 
proc.Close()

You don't need to comment out (remove) the StandardError lines, but it might make more sense to do so.

[giodepa]

Hi Inferrd,
no there is no reason to use pipe character, just I wanted to generate a dos command error and capture it in order to show it on richtextbox. So I wrongly decided to use pipe character.
With your help, I solved my issue.

thanks
gio

Is there a reason you are using the | character in your command? Are you trying to do something else, that you haven't mentioned, that is also not producing the expected output to the RichTextBox?

I ask since changing your command to something like

proc.StandardInput.WriteLine("cdf")

will produce error text in the RichTextBox as expected.

I never got around to using DOS, so I don't have an answer as to why it's not working with "cd|". However, I believe the | character is the DOS Pipe operator. Could it be that you can't use piping while you are also redirecting standard output/error streams? As an observation, when issuing a command such as

proc.StandardInput.WriteLine("dir C:\Windows\System32 | MORE")

the | MORE seems to be ignored.


On a related note, should you want to display the output from the STDOUT and STDERR streams "simultaneously" (as opposed to any error messages all being tagged on to the very end of your RichTextBox's Text), then you could use the DOS redirect 2>&1 after your command. This would redirect STDERR to STDOUT before STDOUT is redirected to your RichTextBox. I'm sorry to say that it doesn't help with your original problem, though.

Dim start_info As New ProcessStartInfo("cmd.exe")
start_info.UseShellExecute = False
start_info.CreateNoWindow = True
start_info.RedirectStandardOutput = True
' start_info.RedirectStandardError = True
start_info.RedirectStandardInput = True
 
Dim proc As New Process()
proc.StartInfo = start_info
proc.Start()
 
proc.StandardInput.WriteLine("cdf 2>&1")
proc.StandardInput.Close()
 
Dim std_out As StreamReader = proc.StandardOutput()
'  Dim std_err As StreamReader = proc.StandardError()
 
RichTextBox1.Text = std_out.ReadToEnd() ' + std_err.ReadToEnd()
 
std_out.Close()
' std_err.Close()
 
proc.Close()

You don't need to comment out (remove) the StandardError lines, but it might make more sense to do so.