Input file 'order-pref.txt' contains two sql UPDATE commands for each item.
$ cat order-pref.txt
computer networking book
UPDATE orders SET quantity = '5' WHERE id = '9';
UPDATE orders SET quantity = '5' WHERE id = '8';
puzzle and skill games
UPDATE orders SET quantity = '5' WHERE id = '99';
UPDATE orders SET quantity = '5' WHERE id = '98';
arithmetic sequence
UPDATE orders SET quantity = '5' WHERE id = '55';
UPDATE orders SET quantity = '5' WHERE id = '56';
Required:
For each item find and print the first UPDATE sql command (i.e. first occurrence of each set of sql commands for each item).
i.e. required output:
UPDATE orders SET quantity = '5' WHERE id = '9';
UPDATE orders SET quantity = '5' WHERE id = '99';
UPDATE orders SET quantity = '5' WHERE id = '55';
Awk solution:
$ awk '/^UPDATE/{++c;if(c%2==1)print}' order-pref.txt > o.sql
Output:
$ cat o.sql
UPDATE orders SET quantity = '5' WHERE id = '9';
UPDATE orders SET quantity = '5' WHERE id = '99';
UPDATE orders SET quantity = '5' WHERE id = '55';
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Posts
2 comments:
awk ' /^[^U]/{getline;print} ' order-pref.txt
WS="[$(printf " \t\n")]"; # whitespace(space and TAB only) glob expression
set X;
while IFS= <&3 read -r Line; do
case $Line in
'UPDATE'$WS* )
case $# in [1357]) printf '%s\n' "$Line";; esac
set X ${1+"$@"};;
esac
done 3< order-pref.txt
sed -ne '
/^UPDATE\s/!d
G
/\n\(.\{2\}\)*$/P
s/.*\n/./; h
' order-pref.txt
perl -wMstrict -lne 'print if /^UPDATE\s/ && !($a++%2)' order-pref.txt
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