UNIX for Dummies Questions & Answers

$ echo Sample: ABCdefGHiJ | awk '{if($1=="Sample:") print tolower($_)}'
sample: abcdefghij

$ cat sample16.txt
Sample: ABCdefgh
domain: when you think abcd@tester.com
domain: abcdefgh@tester2.com
Goods for purchase:234
domain: efgh@anyother.com
Sample: PQRST
Sample: nmjkl
Sample: 123jjkl Mer.
Goods for purchase: No ChaNGE

$ awk '{if($1=="Sample:") {print tolower($_)} else {print}}' <sample16.txt | sed 's/^sample:/Sample:/'
Sample: abcdefgh
domain: when you think abcd@tester.com
domain: abcdefgh@tester2.com
Goods for purchase:234
domain: efgh@anyother.com
Sample: pqrst
Sample: nmjkl
Sample: 123jjkl mer.
Goods for purchase: No ChaNGE

$  echo  "domain: efgh@anyother.com" | cut -f1 -d"@"
domain: efgh

$ awk -F: '$1=="Sample"{print $1,tolower($2);next}$1=="domain"&&e=index($2,"@"){print $1,substr($2,1,e-1);next}1' OFS=: input
Sample: abcdefgh
domain: when you think abcd
domain: abcdefgh
Goods for purchase:234
domain: efgh
Sample: pqrst
Sample: nmjkl
Sample: 123jjkl mer.
Goods for purchase: No ChaNGE

#!/usr/bin/awk -f
$1=="Sample:"{s=$0;sub(/^[^:]*:/,"",s);print $1 tolower(s);next}
$1=="domain:"&&e=index($0,"@"){print substr($0,1,e-1);next}
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