I like to use tac to reverse the output of cat. However, it's not available in the Mavericks terminal. I tried to find it on MacPorts and again it's not available. Can anyone please show me how to get tac? It's very helpful for reading log files.
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4 Answers
On OS/X like on many systems (BSDs, Solaris, AIX, IRIX...), the functionality of GNU tac is available in tail with the -r option. So no need to install GNU tac:
tail -r the-file
answered Feb 7, 2014 at 15:03
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12Well, actually using a shell alias may fail because aliases don't transfer into shell scripts. Use a function like
tac() { tail -r -- "$@"; }– kojiroMar 1, 2016 at 17:44 -
Does it have options like
-rswhich will let you reverse at char level instead of new lines?– C--Nov 7, 2019 at 20:00 -
@SubinSebastian, I've updated the link to the man page which Apple no longer makes available. But in short, no BSD
tailhas no equivalent of GNUtac's-soption. Nov 7, 2019 at 21:45
Yes:
- Install Homebrew
brew install coreutilsln -s /usr/local/bin/gtac /usr/local/bin/tac
or use MacPorts to install coreutils in a similar way.
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2Addition to grebneke's answer: no need the soft link anymore. The g suffix is now only added if osx already has a command with that name, so tac is installed as tac, not gtac. Feb 17, 2019 at 21:34
One temporary solution could be:
alias tac='perl -e "print reverse(<>)"'
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1This just caused me to learn that
<>doesn't only read from STDIN, but optionally from@ARGV. stackoverflow.com/questions/29020883/… I still don't know ifreversewill load the whole file into memory before outputting the lines in reverse order. That would be terrible. Apr 9, 2019 at 18:11 -
1@BrunoBronosky, > ...STDIN, but optionally from @ ARGV : yes that is what <> is for. > ... will load the whole file into memory... : YES, IT WILL! (avoid doing this with gigabyte files)– JJoaoApr 10, 2019 at 7:45
Install gnu coreutils already compiled with Rudix:
sudo rudix install coreutils
Or download and gui install Rudix coreutils
