Collaboration diagram for Handling extended attributes:

Extended attributes can be written, tested and copied by ewmscp.

Attributes written by ewmscp

Attributes can be written during the copy process, which means they are set on the input file after it was opened for reading before reading starts and are removed again when the copy has finished, they will remain if the copy fails. This set of attributes is controlled by the –process-source-attrs option.
At the start of the copy process (after opening the source file, before starting to read) another set of attributes, controlled by –start-source-attrs is written and kept.

When the copy process is done there are two different actions, depending on the outcome.

If the copy went well: On the source file the –success-source-attrs are set and any old –failure-source-attrs are removed. On the destination file the –success-dest-attrs are written. This happens before the destination file is renamed to it final name (relevant for backup mode after)
If the copy went bad: On the source file the –failure-source-attrs are written. Because in case of failure there will be no destination file (partially failed copies are removed) no attributes will be written.

Attributes checked by ewmscp

before the start of a copy the – prohibitive-attrs are checked. If any of them is set the file will not be touched at all.
if any of the –append-attrs are set, additionally the file name matches the appendable files regxexp and the output file already exists ans is smaller than the source file just the additional part of the source file is appended.
after the copy is done, but before the result file is closed the –check-source-attrs are checked on the source file. If one of them is missing or the current value is different from the value from the source file the copy is discarded an an error is flagged. This can be used to only copy files that still match their original check sum.

the value of an extended attribute: If the value part of an attribute has the form %keyword it is exanded, Expansion of key words in attributes

extended attribute copy: if the –preserve option contains all or attr the extended attributes of the source file are copied to the result file. preservables