Find a file along the Windows PATH variable

function/S FindFileAlongWindowsPath(fileNameAndExt)
string fileNameAndExt
 
    string tmpDir = SpecialDirPath("Temporary", 0, 1, 0), tmpFile = "FindFileAlongWindowsPath.txt"
    string tmpFileWinPath = "\"" + ReplaceString("\\",tmpDir, "\\\\") + tmpFile + "\""  // double "\" escaping imposed by Igor
    string cmdPattern = "cmd /c \"%s\"", cmd, result
    variable refnum
 
    // 1. Let Windows find the file in the paths present in the PATH variable 
    // We use a trick by employing the "enhanced substitution of FOR variable references" feature.
    // Documentation of the "FOR /F" command can be found, e.g., at <http://www.pc-ask.com/xp-dos/xp-dos-cmd.html>.
    // The argument to "@echo" has a leading "." to avoid getting gibberish in case the file is not found.
    sprintf cmd, cmdPattern, "for /f %Z in (\"" + fileNameAndExt + "\") do @echo .%~$path:Z > " + tmpFileWinPath
    ExecuteScriptText/B cmd
 
    // 2. Read back the result
    Open refnum as tmpDir+tmpFile   // since "Igor currently cannot read from a console application's standard output"
    FReadLine refnum, result            // we wrote the result to a temprorary file and read that in here
    Close refnum
    
    // 3. Clean up temporary file
    sprintf cmd, cmdPattern, "del " + tmpFileWinPath
    ExecuteScriptText/B cmd
 
    return result[1,strlen(result)-3]   // remove leading "." and trailing " \n"; returns empty string if file not found.
end