awk printing the second to last record of a file - awk

Question

I have a file set up like
Words on
many line
%
More Words
on many lines
%
Even More Words
on many lines
%
and I would like to output the second to last record of this file where the record is delimited by % after each block of text.
I have used:
awk -v RS=\% ' END{ print NR }' $f
to find the number of records (1136). Then I did
awk -v RS=\% ' { print $(NR-1) }' $f
and
awk -v RS=\% ' { print $(NR=1135) }' $f
.
Neither of these worked, and, instead, displayed a record towards the beginning of the file and a many blank lines.
OUTPUT:
"You know, of course, that the Tasmanians, who never committed adultery, are
now extinct."
-- M. Somerset Maugham
"The
is
what
that
This output had many, many more blank lines and contains a record near the middle of the file.
awk -v RS=\% 'END{ print $(NR-1) }' $f
returns a blank line. The same command with different $(NR-x) values also returns a blank line.
Can someone help me to print the second to last record in this case?
Thanks

Answer 1

You can do:
awk '{this=last;last=$0} END{print this}' file
Or, if you don't mind having the entire file in memory:
awk '{a[NR]=$0} END{print a[NR-1]}' file
Or, if it is just line count (or record count) based, you can keep a rolling deletion going so you are not too piggish on memory:
$ seq 999999 | tail -2
999998
999999
$ seq 999999 | awk '{a[NR]=$0; delete a[NR-3]} END{print a[NR-1]}'
999998
If they are blocks of text the same method works if you can separate the blocks into delimited records.
Given:
$ echo "$txt"
Words on
many line
%
More Words
on many lines
%
Even More Words
on many lines
%
You can do:
$ echo "$txt" | awk -v RS=\% '{a[NR]=$0} END{print a[NR-1]}'
Even More Words
on many lines
$ echo "$txt" | awk -v RS=\% '{a[NR]=$0} END{print a[NR-2]}'
More Words
on many lines
If you want to not print the leading and trailing \n you can do:
$ echo "$txt" | awk 'BEGIN{RS="%\n"} {a[NR]=$0} END{printf a[NR-2]}'
Words on
many line
Finally, if you know the specific record you want to print, do it this way in awk:
$ seq 999999 | awk -v mrk=1135 'NR==mrk{print; exit}'
1135
If you want a random record, you can do:
$ awk -v min=1 -v max=1135 'BEGIN{srand()
RS="%\n"
tgt=int(min+rand()*(max-min+1))
}
NR==tgt{print; exit}' file

Answer 2

Does the solution have to be with awk? Just using head and tail would be simpler.
tail -2 file.txt | head 1 > justthatline.txt

Answer 3

The best way for this would be to use the BEGIN construct.
awk 'BEGIN{RS="%\n"; ORS="%\n"}(NR>=2){print}' file
RS and ORS set the input file and output record separators respectively.