cool sed tricks 
Remove Blank Lines from file
     cat file-blanklines-2-be-deleted | sed -e '/^$/d' | tee newfile-no-blanklines

 some "sed-like" tricks from within vi: 


 insert # at beginning of lines 


:%s/.*/# &/g   - inserts a # at the beginning of every line


:15,$s/.*/# &/g   - inserts a # at the beginning of line 15, until the end of the file


:15,250s/.*/# &/g   - inserts a # from line 15 through 250.


 turn one or more blank spaces into one space
	:%s/  */ /g


 remove blank lines, or lines with only spaces or tabs
	:g/^[ t]*$/d  --> WHERE t=tab


 redo entire line adding parentheses: 
  at command line: 	sed s/.*/( & )/  file > new.file
	 	or
         from within vi:	:%s/.*/( & )/g 
 create a list of commands from a directory listing: 

 ls > list
	cat list:
		list
		sed.html
		file.txt
 sed 's/.*/mv & &.save/' list > list2mv  
	cat list2mv:
		mv list list.save
		mv sed.html sed.html.save
		mv file.txt file.txt.save
 rm list
 chmod 750 list2mv
 ./list2mv (to move files to *.save version, could use cp to make backup copies)

 delete blank spaces: 
     FROM within vi:
         :%s/^  *\(.*\)/\1/g    OR
   	    :%s$^  *\(.*\)$\1$g

 delete blank lines: 
            sed  /^$/d  file > newfile
     FROM within vi:
               :g/^$/d  or :%s/^$/d
 some "sed-like" tricks using  perl at the command line: 

perl -pi -e 's/.*/# &/g' filename - inserts a # at the beginning of every line
  (FOR SOME REASON THE ABOVE COMMAND worked yesterday, but not today...  but
the command does work in vi, so I must have goofed...  I remember having some
notes on why it doesn't work... I'll fix this later... john. :)

  note: to do specific lines in perl gets a bit ugly...  (as far as I know at this point)

perl -pi'*.bak' -e 'if ($.==3){s/$_/Replacement text/;}' file.txt
        3 is the line affected
    (this might work at the command line, ymmv - tested on HP)

perl -pi'*.bak' -e 'if ($.==3..20){s/$_/Replacement text/;}' file.txt
 	3 through 20 would be affected