How to return an environment variable? [modified]
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I cannot get my environment variables to return a value in the message box in this example, but it works fine with things like "ipconfig" ... any idea as to why?
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;namespace WindowsFormsApplication4
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();} private void Form1\_Load(object sender, EventArgs e) { string testSession = ExecuteCommandSync("sessionname"); MessageBox.Show(testSession); } public string ExecuteCommandSync(object command) { try { // create the ProcessStartInfo using "cmd" as the program to be run, // and "/c " as the parameters. // Incidentally, /c tells cmd that we want it to execute the command that follows, // and then exit. System.Diagnostics.ProcessStartInfo procStartInfo = new System.Diagnostics.ProcessStartInfo("cmd", "/c " + command); // The following commands are needed to redirect the standard output. // This means that it will be redirected to the Process.StandardOutput StreamReader. procStartInfo.RedirectStandardOutput = true; procStartInfo.UseShellExecute = false; // Do not create the black window. procStartInfo.CreateNoWindow = false; // Now we create a process, assign its ProcessStartInfo and start it System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.StartInfo = procStartInfo; proc.Start(); // Get the output into a string string result = proc.StandardOutput.ReadToEnd(); //string result2 = System.Diagnostics.ProcessStartInfo( //procStartInfo("cmd", "/c " + command); return (result); // Display the command output. } catch (Exception objException) { // Log the exception return("failure"); } } }}
Strangely enough when I do this through a console app it works and when the environment variable changes I cannot see the change until I close the program and reopen another instance of it? Then it displays the change in the environment variable. Why is that?
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I cannot get my environment variables to return a value in the message box in this example, but it works fine with things like "ipconfig" ... any idea as to why?
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;namespace WindowsFormsApplication4
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();} private void Form1\_Load(object sender, EventArgs e) { string testSession = ExecuteCommandSync("sessionname"); MessageBox.Show(testSession); } public string ExecuteCommandSync(object command) { try { // create the ProcessStartInfo using "cmd" as the program to be run, // and "/c " as the parameters. // Incidentally, /c tells cmd that we want it to execute the command that follows, // and then exit. System.Diagnostics.ProcessStartInfo procStartInfo = new System.Diagnostics.ProcessStartInfo("cmd", "/c " + command); // The following commands are needed to redirect the standard output. // This means that it will be redirected to the Process.StandardOutput StreamReader. procStartInfo.RedirectStandardOutput = true; procStartInfo.UseShellExecute = false; // Do not create the black window. procStartInfo.CreateNoWindow = false; // Now we create a process, assign its ProcessStartInfo and start it System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.StartInfo = procStartInfo; proc.Start(); // Get the output into a string string result = proc.StandardOutput.ReadToEnd(); //string result2 = System.Diagnostics.ProcessStartInfo( //procStartInfo("cmd", "/c " + command); return (result); // Display the command output. } catch (Exception objException) { // Log the exception return("failure"); } } }}
Where in your code sample are you reading an environement variable? When asking why something is broken, show us the broken thing that is applicable, not some other thing that works fine. You do understand that each cmd process has its own environment right?
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I cannot get my environment variables to return a value in the message box in this example, but it works fine with things like "ipconfig" ... any idea as to why?
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;namespace WindowsFormsApplication4
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();} private void Form1\_Load(object sender, EventArgs e) { string testSession = ExecuteCommandSync("sessionname"); MessageBox.Show(testSession); } public string ExecuteCommandSync(object command) { try { // create the ProcessStartInfo using "cmd" as the program to be run, // and "/c " as the parameters. // Incidentally, /c tells cmd that we want it to execute the command that follows, // and then exit. System.Diagnostics.ProcessStartInfo procStartInfo = new System.Diagnostics.ProcessStartInfo("cmd", "/c " + command); // The following commands are needed to redirect the standard output. // This means that it will be redirected to the Process.StandardOutput StreamReader. procStartInfo.RedirectStandardOutput = true; procStartInfo.UseShellExecute = false; // Do not create the black window. procStartInfo.CreateNoWindow = false; // Now we create a process, assign its ProcessStartInfo and start it System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.StartInfo = procStartInfo; proc.Start(); // Get the output into a string string result = proc.StandardOutput.ReadToEnd(); //string result2 = System.Diagnostics.ProcessStartInfo( //procStartInfo("cmd", "/c " + command); return (result); // Display the command output. } catch (Exception objException) { // Log the exception return("failure"); } } }}
Like T M Gray said already... Where are you actually getting an environment variable in this code? And if that's your goal, why not just do it the easy way?
string something = Environment.GetEnvironmentVariable("something");
Not really sure what launching command-line processes and redirecting I/O has to do with environment variables...
Proud to have finally moved to the A-Ark. Which one are you in?
Author of the Guardians Saga (Sci-Fi/Fantasy novels) -
I cannot get my environment variables to return a value in the message box in this example, but it works fine with things like "ipconfig" ... any idea as to why?
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;namespace WindowsFormsApplication4
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();} private void Form1\_Load(object sender, EventArgs e) { string testSession = ExecuteCommandSync("sessionname"); MessageBox.Show(testSession); } public string ExecuteCommandSync(object command) { try { // create the ProcessStartInfo using "cmd" as the program to be run, // and "/c " as the parameters. // Incidentally, /c tells cmd that we want it to execute the command that follows, // and then exit. System.Diagnostics.ProcessStartInfo procStartInfo = new System.Diagnostics.ProcessStartInfo("cmd", "/c " + command); // The following commands are needed to redirect the standard output. // This means that it will be redirected to the Process.StandardOutput StreamReader. procStartInfo.RedirectStandardOutput = true; procStartInfo.UseShellExecute = false; // Do not create the black window. procStartInfo.CreateNoWindow = false; // Now we create a process, assign its ProcessStartInfo and start it System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.StartInfo = procStartInfo; proc.Start(); // Get the output into a string string result = proc.StandardOutput.ReadToEnd(); //string result2 = System.Diagnostics.ProcessStartInfo( //procStartInfo("cmd", "/c " + command); return (result); // Display the command output. } catch (Exception objException) { // Log the exception return("failure"); } } }}
Because if you define a variable in another process, it won't exist in this one. :mad:
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Where in your code sample are you reading an environement variable? When asking why something is broken, show us the broken thing that is applicable, not some other thing that works fine. You do understand that each cmd process has its own environment right?
I am asking for sessionname I had to replace ipconfig with sessionname in my original post, sorry about the confusion.
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Like T M Gray said already... Where are you actually getting an environment variable in this code? And if that's your goal, why not just do it the easy way?
string something = Environment.GetEnvironmentVariable("something");
Not really sure what launching command-line processes and redirecting I/O has to do with environment variables...
Proud to have finally moved to the A-Ark. Which one are you in?
Author of the Guardians Saga (Sci-Fi/Fantasy novels)Hi, I tried that, and when I have a form that has a button/messagebox to check that and then display it, it keeps displaying the outdated variable value?
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Because if you define a variable in another process, it won't exist in this one. :mad:
Hi, I'm not setting it, it will change by the OS ... but when I call it after the change it still does not display the new value?
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I cannot get my environment variables to return a value in the message box in this example, but it works fine with things like "ipconfig" ... any idea as to why?
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;namespace WindowsFormsApplication4
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();} private void Form1\_Load(object sender, EventArgs e) { string testSession = ExecuteCommandSync("sessionname"); MessageBox.Show(testSession); } public string ExecuteCommandSync(object command) { try { // create the ProcessStartInfo using "cmd" as the program to be run, // and "/c " as the parameters. // Incidentally, /c tells cmd that we want it to execute the command that follows, // and then exit. System.Diagnostics.ProcessStartInfo procStartInfo = new System.Diagnostics.ProcessStartInfo("cmd", "/c " + command); // The following commands are needed to redirect the standard output. // This means that it will be redirected to the Process.StandardOutput StreamReader. procStartInfo.RedirectStandardOutput = true; procStartInfo.UseShellExecute = false; // Do not create the black window. procStartInfo.CreateNoWindow = false; // Now we create a process, assign its ProcessStartInfo and start it System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.StartInfo = procStartInfo; proc.Start(); // Get the output into a string string result = proc.StandardOutput.ReadToEnd(); //string result2 = System.Diagnostics.ProcessStartInfo( //procStartInfo("cmd", "/c " + command); return (result); // Display the command output. } catch (Exception objException) { // Log the exception return("failure"); } } }}
How are you checking the value? I'm not sure if this changed in the latest versions of Windows, but usually environment variables are initialized with a copy of the OS environment variables when the process starts. While the process is running, any changes in environment variables via the OS would not be seen by the process and any changes made to variables in the process will not be passed back to the OS.
CQ de W5ALT
Walt Fair, Jr., P. E. Comport Computing Specializing in Technical Engineering Software
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How are you checking the value? I'm not sure if this changed in the latest versions of Windows, but usually environment variables are initialized with a copy of the OS environment variables when the process starts. While the process is running, any changes in environment variables via the OS would not be seen by the process and any changes made to variables in the process will not be passed back to the OS.
CQ de W5ALT
Walt Fair, Jr., P. E. Comport Computing Specializing in Technical Engineering Software
Hi Walt, I've checked it both with the code above and by just calling the environment variable with a get environment variable call. Both times the code will not reflect the change until I restart the application I am building. I know the variable is changing though, because I can open a cmd prompt and type %sessionname% and it will reflect whether I am logged in locally or via console mode. I tried to keep spawning a new cmd prompt window within a form, so that it would close and then reopen the window and write the %sessionname% value, but closing the cmd window seems to kill my do while loop and I couldn't get around that even after 3 hours of trial and error :)
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Hi Walt, I've checked it both with the code above and by just calling the environment variable with a get environment variable call. Both times the code will not reflect the change until I restart the application I am building. I know the variable is changing though, because I can open a cmd prompt and type %sessionname% and it will reflect whether I am logged in locally or via console mode. I tried to keep spawning a new cmd prompt window within a form, so that it would close and then reopen the window and write the %sessionname% value, but closing the cmd window seems to kill my do while loop and I couldn't get around that even after 3 hours of trial and error :)
Yes, that's what I would expect. The environment variables in your process and the OS and any other process are meant to be totally independent so that total chaos in the OS won't ensue. When you spawn your process (cmd window, etc.) it starts with a copy of the owner's environment variables, but any changes it makes are local to your process (cmd window) and any changes made in another process (a new cmd window or the OS) will not be seen by your process. I think you have confirmed that that's exactly what is happening. If you need to pass changeable information between processes, environment variables are not the solution. They are meant to be used for more or less static system information.
CQ de W5ALT
Walt Fair, Jr., P. E. Comport Computing Specializing in Technical Engineering Software
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Yes, that's what I would expect. The environment variables in your process and the OS and any other process are meant to be totally independent so that total chaos in the OS won't ensue. When you spawn your process (cmd window, etc.) it starts with a copy of the owner's environment variables, but any changes it makes are local to your process (cmd window) and any changes made in another process (a new cmd window or the OS) will not be seen by your process. I think you have confirmed that that's exactly what is happening. If you need to pass changeable information between processes, environment variables are not the solution. They are meant to be used for more or less static system information.
CQ de W5ALT
Walt Fair, Jr., P. E. Comport Computing Specializing in Technical Engineering Software
Hi Walt, I thought it would load the environment variables in real time, not each time the program launches but that would explain my results. What would you suggest to monitor sessionname status? I'd ultimately like to create a service that runs under the local system account and monitors what type of connection someone is logged in under, be it console or RTP. Any suggestions?
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Hi Walt, I thought it would load the environment variables in real time, not each time the program launches but that would explain my results. What would you suggest to monitor sessionname status? I'd ultimately like to create a service that runs under the local system account and monitors what type of connection someone is logged in under, be it console or RTP. Any suggestions?
Well, I'm no expert on the topic of inter-process communications! If everything is running on a single machine, I'd probably take the chicken way out and use a simple file to save information. But I suspect a true service would be much better and probably more scalable.
CQ de W5ALT
Walt Fair, Jr., P. E. Comport Computing Specializing in Technical Engineering Software