saving a file after SED
 

when i run the sed , it replaces the text but it doesnot save that edited file, how can i replace the existing file with the edited file using sed

You should redirect the output to a temp file and then ovewrite original file with the temp one:

Use sed's -i flag. Be careful, there's no way back.

Yves.

You can supply a suffix to -i which will cause a backup to be created (with GNU sed at least).