-the CALLOUT program returned string
-(this does not work within the PROGRAM field for the obvious reason.)
-.TP
-.B %D
-Use the devfs style disk name for this device.
-For partitions, this will result in 'part%n'
-If this is not a partition, it will result in 'disk'
-.RE
+The string returned by the external program, specified in
+.B PROGRAM
+(This does not work within the
+.B PROGRAM
+field for the obvious reason.)
+.br
+A single part of the string, separated by a space character
+may be selected by specifying the part number as an attribute:
+.BI %c{ N }
+If the number is followed by the + char this part plus
+all remaining parts of the result string are substituted:
+.BI %c{ N+ }
+.TP
+.B %N
+The name of a created temporary device node to provide access to the
+device from a external program.
+.TP
+.B %P
+The node name of the parent device.
+.TP
+.BI %s{ filename }
+The content of a sysfs attribute.
+.TP
+.B %r
+The udev_root value.
+.TP
+.B %e
+If a device node already exists with the name, the smallest positive
+decimal integer N is substituted such that the resulting name doesn't
+match an existing device node. Otherwise nothing is substituted. This
+can be used to create compatibility symlinks and enumerate devices of
+the same type originating from different kernel subsystems.
+.sp
+Note: The use of the enumeration facility is unreliable outside of
+udevstart where the node creation is serialized and predictable.
+The returned numbers rely on the order devices are probed on the
+system. If more than one device requests an enumeration for the same
+name at the same time, it may be possible that both requests receive the
+same name back from the database. The use of enumerations in todays setups
+where device can come and go at any time is not recomended.
+.TP
+.B %%
+The '%' character itself.
+.P
+The count of characters to insert may be limited by specifying
+the format length value. For example, '%3s{file}' will only insert
+the first three characters of the sysfs attribute.