The user type is used to look up passwd(5) information using the method defined by the MailboxDatabase option (MailboxDatabase). A password entry typically looks like this:

ftp:*:1092:255:File Transfer Protocol Program:/u/ftp:/bin/sh

Here, there are seven fields, each separated from the others by colon characters. The key is always compared to the first field. The value returned is (by default) the first field unless you specify another field with a -v switch:

Kname user -vfield 

Here, field can be either a number 1 through 7, or one of the names name, passwd, uid, gid, gecos, dir, or shell, which correspond to the numbers. For example, to look up usernames and get the full name (GECOS) field returned, you could use something such as this:

Kgetgecos user -vgecos
...
R$-        $: $( getgecos $1 $)

Note that this returns the full GECOS field in its rawest form. It is not cleaned up to provide a reliable full name, as is the $x macro ($x).

The user database-map type can be used in conjunction with the Local_check_rcpt rule set (Section 7.1.3). In the following, for example, we check to see whether a recipient is a local user and, if so, reject the user if that user's home directory is /home/retired/tars:

Kislocal user -vdir

SLocal_check_rcpt
R$*                        $: $>canonify $1        focus on host
R$* <@ $+ > $*             $: $1                   discard host
R$+                        $: $1 $(islocal $1 $)
R$- /home/retired/tars     $#error $@ 5.1.3 $: 553 Sorry, $1 is retired, no forwarding

Here, we focus on the host part with the canonify rule set 3, then discard all but the user part in the second rule. The third rule performs the lookup. If the user is not found, that username is returned unchanged. If, on the other hand, the user is found, that user's name and home directory are placed into the workspace. The last rule rejects any SMTP RCPT command that contains a local-user part whose home directory is /home/retired/tars.

Only a few database switches are useful with this user type. All are listed in Table 23-28.

This user database-map type can be watched with the -d38.20 debugging command-line switch (-d38.20).