File: sed.info,  Node: Centering lines,  Next: Increment a number,  Prev: Joining lines,  Up: Examples

7.2 Centering Lines
===================

This script centers all lines of a file on a 80 columns width.  To
change that width, the number in ‘\{...\}’ must be replaced, and the
number of added spaces also must be changed.

   Note how the buffer commands are used to separate parts in the
regular expressions to be matched--this is a common technique.

     #!/usr/bin/sed -f

     # Put 80 spaces in the buffer
     1 {
       x
       s/^$/          /
       s/^.*$/&&&&&&&&/
       x
     }

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

     # add a newline and 80 spaces to end of line
     G

     # keep first 81 chars (80 + a newline)
     s/^\(.\{81\}\).*$/\1/

     # \2 matches half of the spaces, which are moved to the beginning
     s/^\(.*\)\n\(.*\)\2/\2\1/