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 path.

If I want to start notepad, I can use

Process.Start("notepad.exe");

instead of

Process.Start(@"c:\windows\system32\notepad.exe");

because the directory c:\windows\system32 is part of the PATH environment variable.

how can I check if a file exists on the PATH without executing the process and without parsing the PATH variable?

System.IO.File.Exists("notepad.exe"); // returns false
(new System.IO.FileInfo("notepad.exe")).Exists; // returns false

but I need something like this:

System.IO.File.ExistsOnPath("notepad.exe"); // should return true

and

System.IO.File.GetFullPath("notepad.exe"); // (like unix which cmd) should return
                                           // c:\windows\system32\notepad.exe

Is there a predefined class to do this task available in the BCL?

Answer 1

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;
}