delete line if string is matched and the next line contains another string - awk

Question

got an annoying text manipulation problem, i need to delete a line in a file if it contains a string but only if the next line also contains another string. for example, i have these lines:
john paul
george
john paul
12
john paul
i want to delete any line containing 'john paul' if it is immediately followed by a line that contains 'george', so it would return:
george
john paul
12
john paul
not sure how to grep or sed this. if anyone could lend a hand that'd be great!

Answer 1

This might work for you (GNU sed):
sed '/john paul/{$!N;/\n.*george/!P;D}' file
If the line contains john paul read the next line and if it contains george don't print the first line.
N.B. If the line containing george contains john paul it will be checked also.

Answer 2

awk 'NR > 1 && !(/george/ && p ~ /john paul/) { print p } { p = $0 } END { print }' file
Output:
george
john paul
12
john paul

Answer 3

This awk should do:
cat file
john paul
george
john paul
12
john paul
hans
george
awk 'f~/john paul/ && /george/ {f=$0;next} NR>1 {print f} {f=$0} END {print}' file
george
john paul
12
john paul
hans
george
This will only delete name above george if it is john paul

Answer 4

Here is one version more general:
if the lines matches a string and previous line was exactly "john paul" then do nothing, otherwise, print the previous line. (change the ^[a-zA-Z]$ part to george if you only want george to be detected.
awk '!(/^[a-zA-W]+$/ && previous ~/^john paul$/){print previous}{previous=$0}END{print}'
In your example:
$> echo 'john paul
george
john paul
12
john paul' |awk '!(/^[a-zA-W]+$/ && previous ~/^john paul$/){print previous}{previous=$0}END{print}'
george
john paul
12
john paul
if there is some numbers in the line, it prints the previous, otherwise it doesn't:
$> echo 'john paul
george 234
john paul
auie
john paul' |awk '!(/^[a-zA-W]+$/ && previous ~/^john paul$/){print previous}{previous=$0}END{print}'
john paul
george 234
auie
john paul

Answer 5

The sed solution is short: two commands and lots of comments ;)
/john paul/ {
# read the next line and append to pattern space
N
# and then if we find "george" in that next line,
# only retain the last line in the pattern space
s/.*\n\(.*george\)/\1/
# and finally print the pattern space,
# as we don't use the -n option
}
You put the above in some sedscript file and then run:
sed -f sedscript your_input_file

Answer 6

Just to throw some Perl into the mix:
perl -ne 'print $p unless /george/ && $p =~ /john paul/; $p = $_ }{ print $p' file
Print the previous line, unless the current line matches /george/ and the previous line $p matched /john paul/. Set $p to the value of the previous line. }{ effectively creates an END block, so the last line is also printed after the file has been read.

Answer 7

You might have to change the \r\n to \n or to \r, other than that this should work:
<?php
$string = "john paul
george
john paul
12
john paul";
$string = preg_replace("#john paul\r\n(george)#i",'$1',$string);
echo $string;
?>
You could also read a file into the variable and then after overwrite the file.

Answer 8

With GNU awk for multi-char RS:
$ gawk -vRS='^$' '{gsub(/john paul\ngeorge/,"george")}1' file
george
john paul
12
john paul
or if there's more on each line than your sample input shows just change the RE to suit and use gensub():
$ gawk -vRS='^$' '{$0 = gensub(/[^\n]*john paul[^\n]*\n([^\n]*george[^\n]*)/,"\\1","")}1' file
george
john paul
12
john paul