Fmt

fmt is a command that reflows text to make more uniform margins.

Options

 * -s --split-only splits long lines, but does not fill in short ones.
 * -w --width=WIDTH maximum line width
 * -g --goal=WIDTH goal width (default: 93% of width)

There are other options listed on the man page, but the actual effect is unclear.

Provided by
Most (all?) Linux distributions incorporate this from the GNU Coreutils: and use its man page

BUGS

 * Correct operation depends on input with sentences ending with newline or two spaces after the [.?!] terminator.
 * A quick trial showed output that seemed to disagree with the man-page description of some of the options used. Those options are not listed here.
 * The final line of a paragraph can be much longer than the goal if the width allows it.