Re: sed syntex in procmailrc question

Zhiliang <hu <at> animalgenome.org> writes:

> I have a recipe wish 'sed' in one of my Smartlist rc, like:
>
>    sed 's/SUBJET/'"$SUBJ"/g
>
> which works fine.  I forgot where did I copied it from but have been
> puzzled by its syntex with respect to the use of the single quotes
> "'". Following what's described in sed tutorials I made it:
>
>    sed 's/SUBJET/"$SUBJ"/g'
>

I'm certainly not any kind of expert on sed but I think what you may
be seeing is really a shell expansion thing.

You an see the difference by echoing the two setups:

At a shell prompt:

  SUBJ=some2subject

Throw something at the sed recipies:

Then in this test, the variable $SUBJECT is allowed to expand:

  echo SUBJECT| sed 's/SUBJECT/'"$SUBJ/g"
   some2subject

-------        ---------       ---=---       ---------      -------- 

Here the variable $SUBJ is not allowed to expand

  echo SUBJECT| sed 's/SUBJECT/"$SUBJ"/g'
  $SUBJ