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