    Set and unset shell options.
    
    Change the setting of each shell option OPTNAME.  Without any option
    arguments, list all shell options with an indication of whether or not each
    is set.
    
    Options:
      -o	restrict OPTNAMEs to those defined for use with `set -o'
      -p	print each shell option with an indication of its status
      -q	suppress output
      -s	enable (set) each OPTNAME
      -u	disable (unset) each OPTNAME
    
    Exit Status:
    Returns success if OPTNAME is enabled; fails if an invalid option is
    given or OPTNAME is disabled.
