def _search_on_path(filenames):
    """Find file on system path."""
    from os.path import exists, abspath, join
    from os import pathsep, environ
    search_path = environ['PATH']
    paths = search_path.split(pathsep)
    for path in paths:
        for filename in filenames:
            if exists(join(path, filename)):
                return abspath(join(path, filename))
