How to reverse lines of a text file?

shell command-line filter reverse
Greg Hewgill picture Greg Hewgill · Jan 6, 2009 · Viewed 21.5k times · Source

I'm writing a small shell script that needs to reverse the lines of a text file. Is there a standard filter command to do this sort of thing?

My specific application is that I'm getting a list of Git commit identifiers, and I want to process them in reverse order:

git log --pretty=oneline work...master | grep -v DEBUG: | cut -d' ' -f1 | reverse

The best I've come up with is to implement reverse like this:

... | cat -b | sort -rn | cut -f2-

This uses cat to number every line, then sort to sort them in descending numeric order (which ends up reversing the whole file), then cut to remove the unneeded line number.

The above works for my application, but may fail in the general case because cat -b only numbers nonblank lines.

Is there a better, more general way to do this?

Answer

Vinko Vrsalovic picture Vinko Vrsalovic · Jan 6, 2009

In GNU coreutils, there's tac(1)

Related questions

How do I copy a folder from remote to local using scp?

How do I copy a folder from remote to local host using scp? I use ssh to log in my server. Then, I would like to copy the remote folder foo to local /home/user/Desktop. How do I achieve …

Read More
How do I set a variable to the output of a command in Bash?

I have a pretty simple script that is something like the following: #!/bin/bash VAR1="$1" MOREF='sudo run command against $VAR1 | grep name | cut -c7-' echo $MOREF When I run this script from the command line and pass it …

Read More
How to reload .bash_profile from the command line?

How can I reload .bash_profile from the command line? I can get the shell to recognize changes to .bash_profile by exiting and logging back in but I would like to be able to do it on demand.

Read More