sendmail, 4th Edition

Return a Selection: $#

The $# operator in the RHS is copied as is into the workspace and functions as a flag advising sendmail that an action has been selected. The $# must be the first token copied into the rewritten workspace for it to have this special meaning. If it occupies any other position in the workspace, it loses its special meaning:

 $# local ← selects delivery agent in the parse rule set 0
 $# OK ← accepts a message in the Local_check_mail rule set
 xxx $# local ← no special meaning

When it is used in the parse rule set 0 (The parse Rule Set 0 on page 696) and localaddr rule set 5 (The localaddr Rule Set 5 on page 700) (and occupies the first position in the rewritten workspace), the $# operator tells sendmail that the second token in the workspace is the name of a delivery agent (here, local). When used in the check_ rule sets (Check Headers with Rule Sets on page 265 and The Local_check_ Rule Sets on page 252) subsequent tokens in the workspace (here, OK) say how a message should be handled.

Note that the $# operator can be prefixed with a $@ or a $: without losing its special meaning because those prefix operators are not copied to the workspace:

 $@ $# local rewritten as → $# local

However, those prefix operators are not necessary because the $# acts just like a $@ prefix. It prevents the LHS from attempting to match again after the RHS rewrite, and it causes any following rules (in that rule set) to be skipped. When used in non-prefix roles in the parse rule set 0 and ...