rsync xxx yyy
ret=$?
if [ $ret -ne 0 ]; then
    echo "失败, 错误码: $ret"
fi
  
rsync常用的错误代码：
0      Success
1      Syntax or usage error
2      Protocol incompatibility
3      Errors selecting input/output files, dirs
4      Requested action not supported: an attempt was made to manipulate 64-bit files on a platform that cannot support them; or an option was specified that is supported by the client and not by the server.
5      Error starting client-server protocol
6      Daemon unable to append to log-file
10     Error in socket I/O
11     Error in file I/O
12     Error in rsync protocol data stream
13     Errors with program diagnostics
14     Error in IPC code
20     Received SIGUSR1 or SIGINT
21     Some error returned by waitpid()
22     Error allocating core memory buffers
23     Partial transfer due to error
24     Partial transfer due to vanished source files
25     The --max-delete limit stopped deletions
30     Timeout in data send/receive