How can I reverse the lines in a file?

Question

I'd like to reverse the lines in a text file (or stdin), preserving the contents of each line.

So, ie, starting with:

foo
bar
baz

I'd like to end up with

baz
bar
foo

Is there a standard unix commandline utility for this?

Answer 1

Yes:

 tail -r myfile.txt

Reference

Answer 2

Also worth mentioning: tac (the, ahem, reverse of cat). Part of coreutils.

Answer 3

There's the well-known sed tricks:

# reverse order of lines (emulates "tac")
# bug/feature in HHsed v1.5 causes blank lines to be deleted
sed '1!G;h;$!d'               # method 1
sed -n '1!G;h;$p'             # method 2

(Explanation: prepend non-initial line to hold buffer, swap line and hold buffer, print out line at end)

If you can't remember that,

perl -e 'print reverse <>'

On a system with GNU utilities, the other answers are simpler, but not all the world is GNU/Linux...

Answer 4

You can do it using a combination of tail and head :)

file=$1
lineCount=`cat $file | wc -l`
counter=0
while [ $counter -le $lineCount ]
do
    tail -$counter $file | head -1
    counter=`expr $counter + 1`
done

Answer 5

grep -n "" myfile.txt | sort -r -n | gawk -F : "{ print $2 }"