what is the field separator on the file now?
if it is a tab, you can do something like this
this will replace all of the tab fields with pipes (this is in vi)
or if it is a space same thing
If the source of your flatfile is NOT data extracted from an Informix table via SQL, that is, you received the flat file from some other source, you could use the streams editor (sed) from a command line prompt.
sed 's/ /|/g' original_flatfile > new_flatfile <cr>
This'll change every occurance of a blank space on every line in the file to a piping symbol. It will work so long as there are no embedded spaces in any of the aaaa bbbb cccc dddd eeee ffff column data.
The original file remains unchanged so using sed is a non-destructive
approach to your problem.