Convert strings of initial whitespace, consisting of at least two spaces and/or tabs, to tabs. Read from standard input if given no file or a file named -.
Convert all, not just leading, strings of spaces and tabs.
Convert only leading spaces and tabs. Overrides -a.
nums is a comma-separated list of integers that specify the placement of tab stops. If a single integer is provided, the tab stops are set to every integer spaces. By default, tab stops are eight spaces apart. This option implies -a.