coreutils: Sorting the output

 
 10.1.3 Sorting the output
 -------------------------
 
 These options change the order in which ‘ls’ sorts the information it
 outputs.  By default, sorting is done by character code (e.g., ASCII
 order).
 
 ‘-c’
 ‘--time=ctime’
 ‘--time=status’
      In long format, print the status change timestamp (the ctime)
      instead of the mtime.  When sorting by time or when not using long
      format, sort according to the ctime.  ⇒File timestamps.
 
 ‘-f’
      Produce an unsorted directory listing.  This is equivalent to the
      combination of ‘--all’ (‘-a’), ‘--sort=none’ (‘-U’), ‘-1’,
      ‘--color=none’, and ‘--hyperlink=none’, while also disabling any
      previous use of ‘--size’ (‘-s’).
 
 ‘-r’
 ‘--reverse’
      Reverse whatever the sorting method is – e.g., list files in
      reverse alphabetical order, youngest first, smallest first, or
      whatever.  This option has no effect when ‘--sort=none’ (‘-U’) is
      in effect.
 
 ‘-S’
 ‘--sort=size’
      Sort by file size, largest first.
 
 ‘-t’
 ‘--sort=time’
      Sort by modification timestamp (mtime) by default, newest first.
      The timestamp to order by can be changed with the ‘--time’ option.
      ⇒File timestamps.
 
 ‘-u’
 ‘--time=atime’
 ‘--time=access’
 ‘--time=use’
      In long format, print the last access timestamp (the atime).  When
      sorting by time or when not using long format, sort according to
      the atime.  ⇒File timestamps.
 
 ‘--time=mtime’
 ‘--time=modification’
      This is the default timestamp display and sorting mode.  In long
      format, print the last data modification timestamp (the mtime).
      When sorting by time or when not using long format, sort according
      to the mtime.  ⇒File timestamps.
 
 ‘--time=birth’
 ‘--time=creation’
      In long format, print the file creation timestamp if available,
      falling back to the file modification timestamp (mtime) if not.
      When sorting by time or when not using long format, sort according
      to the birth time.  ⇒File timestamps.
 
 ‘-U’
 ‘--sort=none’
      Do not sort; list the files in whatever order they are stored in
      the directory.  (Do not do any of the other unrelated things that
      ‘-f’ does.)  This can be useful when listing large directories,
      where sorting can take some time.
 
 ‘-v’
 ‘--sort=version’
      Sort by version name and number, lowest first.  It behaves like a
      default sort, except that each sequence of decimal digits is
      treated numerically as an index/version number.  ⇒Version sort
      ordering.
 
 ‘--sort=width’
      Sort by printed width of file names.  This can be useful with the
      ‘--format=vertical’ (‘-C’) output format, to most densely display
      the listed files.
 
 ‘-X’
 ‘--sort=extension’
      Sort directory contents alphabetically by file extension
      (characters after the last ‘.’); files with no extension are sorted
      first.