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Today I've come across this command for extracting domain name from domain controller's FQDN:

DOMAIN_NAME=$(echo $DC_PC | sed -r 's!^[^.]+\.!!')

What is the meaning of these exclamation marks in sed? How does it work?

marked as duplicate by Thomas Dickey, Archemar, GAD3R, Jeff Schaller, Julie Pelletier Sep 2 '16 at 15:50

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  • That is called as Delimiter in sed – Rahul Sep 2 '16 at 9:58
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    Or just domain_name=${DC_PC#*.} (strictly speaking the equivalent would be ${DC_PC#[!.]*.} because of that + which is I don't think was intended) which would be a lot more portable, efficient and reliable. – Stéphane Chazelas Sep 2 '16 at 10:21

The first character after s is used as the separator for the parameters to s, so this replaces anything matching ^[^.]+\. with the empty string. Traditionally this would be written

sed -r 's/^[^.]+\.//'

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