Check if an executable exists in the Windows path

Question

If I run a process with ShellExecute (or in .net with System.Diagnostics.Process.Start()) the filename process to start doesn\'t need to be a full

Answer 1

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.

/// 

/// 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.
/// 
/// The full path if successful, or null otherwise.
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;