正则表达式用多行代替一行

Question

I have a plain text file in which I need to substitute multiple consecutive lines of text with a single replacement line. For example, when I have a date and time, followed by a blank line, followed by a page number,

11/13/2018 08:33:00

Page 1 of 1

I'd like to replace it with a single line (eg, PAGE BREAK ).

I've tried

sed 's/\d{2}\/\d{2}\/\d{4} \d{2}:\d{2}:\d{2}\n\nPage \d of \d/PAGE BREAK/g' file1.txt > file2.txt

and

perl -pe 's/\d{2}\/\d{2}\/\d{4} \d{2}:\d{2}:\d{2}\n\nPage \d of \d/PAGE BREAK/g' file1.txt > file2.txt

but it leaves the text unchanged.

Answer 1

Both sed and Perl process the input line by line. You can tell Perl to load the whole file into memory by using -0777 (if it's not too large):

perl -0777 -pe 's=[0-9]{2}/[0-9]{2}/[0-9]{4} [0-9]{2}:[0-9]{2}:[0-9]{2}\n\nPage [0-9]+ of [0-9]+=PAGE BREAK=g'

Note that I used [0-9] , because \\d can match ٤, ໖, ६, or 𝟡.

I also used s=== instead of s/// so I don't have to backslash the slashes in the date part.

Answer 2

Another Perl variant

$ cat page_break.txt
123 45 jh kljl
11/13/2018 08:33:00

Page 1 of 1
ghjgjh hkjhj
fhfghfghfh
11/13/2018 08:33:00

Page 1 of 2
ghgigkjkj

$ perl -ne '{ if ( (/\d{2}\/\d{2}\/\d{4} \d{2}:\d{2}:\d{2}/ and $x++)or ( /^\s*$/ and $x++) or (/Page \d of \d/ and $x++) ){} if($x==0) { print "$_" } if($x==3) { print "PAGE BREAK\n"; $x=0} }' page_break.txt
123 45 jh kljl
PAGE BREAK
ghjgjh hkjhj
fhfghfghfh
PAGE BREAK
ghgigkjkj

$