Check if an executable exists in the Windows path
I tried out Dunc's where
process and it works, but it's slow and resource-heavy and there's the slight danger of having an orphaned process.
I like Eugene Mala's tip about PathFindOnPath
, so I fleshed that out as a complete answer. This is what I'm using for our custom in-house tool.
/// <summary>
/// Gets the full path of the given executable filename as if the user had entered this
/// executable in a shell. So, for example, the Windows PATH environment variable will
/// be examined. If the filename can't be found by Windows, null is returned.</summary>
/// <param name="exeName"></param>
/// <returns>The full path if successful, or null otherwise.</returns>
public static string GetFullPathFromWindows(string exeName)
{
if (exeName.Length >= MAX_PATH)
throw new ArgumentException($"The executable name '{exeName}' must have less than {MAX_PATH} characters.",
nameof(exeName));
StringBuilder sb = new StringBuilder(exeName, MAX_PATH);
return PathFindOnPath(sb, null) ? sb.ToString() : null;
}
// https://docs.microsoft.com/en-us/windows/desktop/api/shlwapi/nf-shlwapi-pathfindonpathw
// https://www.pinvoke.net/default.aspx/shlwapi.PathFindOnPath
[DllImport("shlwapi.dll", CharSet = CharSet.Unicode, SetLastError = false)]
static extern bool PathFindOnPath([In, Out] StringBuilder pszFile, [In] string[] ppszOtherDirs);
// from MAPIWIN.h :
private const int MAX_PATH = 260;
This is risky, there's a lot more to it than just searching the directories in the PATH. Try this:
Process.Start("wordpad.exe");
The executable is stored in c:\Program Files\Windows NT\Accessories on my machine, that directory is not on the path.
The HKCR\Applications and HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths keys also play a role in finding executables. I'm fairly sure there are additional land-mines like this around, directory virtualization in 64-bit versions of Windows could trip you up for example.
To make this more reliable I think you need to pinvoke AssocQueryString(). Not sure, never had the need. The better approach is certainly to not have to ask the question.
I think there's nothing built-in, but you could do something like this with System.IO.File.Exists:
public static bool ExistsOnPath(string fileName)
{
return GetFullPath(fileName) != null;
}
public static string GetFullPath(string fileName)
{
if (File.Exists(fileName))
return Path.GetFullPath(fileName);
var values = Environment.GetEnvironmentVariable("PATH");
foreach (var path in values.Split(Path.PathSeparator))
{
var fullPath = Path.Combine(path, fileName);
if (File.Exists(fullPath))
return fullPath;
}
return null;
}
Ok, a better way I think...
This uses the where command, which is available at least on Windows 7/Server 2003:
public static bool ExistsOnPath(string exeName)
{
try
{
using (Process p = new Process())
{
p.StartInfo.UseShellExecute = false;
p.StartInfo.FileName = "where";
p.StartInfo.Arguments = exeName;
p.Start();
p.WaitForExit();
return p.ExitCode == 0;
}
}
catch(Win32Exception)
{
throw new Exception("'where' command is not on path");
}
}
public static string GetFullPath(string exeName)
{
try
{
using (Process p = new Process())
{
p.StartInfo.UseShellExecute = false;
p.StartInfo.FileName = "where";
p.StartInfo.Arguments = exeName;
p.StartInfo.RedirectStandardOutput = true;
p.Start();
string output = p.StandardOutput.ReadToEnd();
p.WaitForExit();
if (p.ExitCode != 0)
return null;
// just return first match
return output.Substring(0, output.IndexOf(Environment.NewLine));
}
}
catch(Win32Exception)
{
throw new Exception("'where' command is not on path");
}
}