tr in bash shell

Any idea what's this line perform ?

tr -cd '[[:digit:]]'`
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Patrick de GelderSupport engineerCommented:
It will extract digits form a string example:

echo "Abc123d56E" | tr -cd '[[:digit:]]'


This should explain it hope it helps,

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AXISHKAuthor Commented:
Tks, what does -cd mean ?

Is it correct for my research listed below ? Tks
-c, -C, --complement
       use the complement of SET1

-d, --delete
       delete characters in SET1, do not translate
Yes, so delete what is not a digit.
Patrick de GelderSupport engineerCommented:
yes that is correct
AXISHKAuthor Commented:
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Shell Scripting

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