#!/usr/bin/sed -f
# center all lines of a file, on a 80 columns width
#
# to change that width, the 2nd number in \{\} must be replaced to w-1

# del leading and trailing spaces
y/	/ /
s/^ *//
s/ *$//

:x
/^.\{1,78\}$/ { s/^.*$/ & /; bx; }

# Remove trailing spaces
s/ *$//