Shell reads File Content

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While read wone wtwo wthree
Do
[-Z $ wone] & continue # test whether the content of this row is empty
Xxx = $ wone # extract content
Done </var/XXX/one.txt
Echo "$ XXX" # The variable obtains the content in the file.

The following methods cannot extract content, but can be output. It seems that the problem lies in how Bash handles pipelines.
(Bash may generate a sub-shell to process pipeline output ).
Bytes ------------------------------------------------------------------------------------------------------------
CAT/var/XXX/one.txt | while read wone wtwo wthree
Do
[-Z $ wone] & continue # test whether the content of this row is empty
Xxx = $ wone # extract content
Done
Echo "$ XXX" # The variable content has not changed.