How can I get the tac command on OS X?

Question

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.

Stéphane Chazelas · Answer 1 · 2019-11-07T21:44:53.397

102

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

edited Nov 07 '19 at 21:44

answered Feb 07 '14 at 15:03

Stéphane Chazelas

544,893

16

So, alias tac='tail -r' will do the trick for OP! – Ketan Feb 07 '14 at 17:18
13

Well, actually using a shell alias may fail because aliases don't transfer into shell scripts. Use a function like tac() { tail -r -- "$@"; } – kojiro Mar 01 '16 at 17:44
Does it have options like -rs which will let you reverse at char level instead of new lines? – C-- Nov 07 '19 at 20:00
@SubinSebastian, I've updated the link to the man page which Apple no longer makes available. But in short, no BSD tail has no equivalent of GNU tac's -s option. – Stéphane Chazelas Nov 07 '19 at 21:45

grebneke · Accepted Answer · 2019-02-19T08:34:27.417

90

Yes:

Install Homebrew
brew install coreutils
~~ln -s /usr/local/bin/gtac /usr/local/bin/tac~~ apparently not needed with latest Homebrew, see comment by Ran Ever-Hadani below

or use MacPorts to install coreutils in a similar way.

edited Feb 19 '19 at 08:34

answered Feb 07 '14 at 14:58

grebneke

4,671

2

Addition 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. – Ran Ever-Hadani Feb 17 '19 at 21:34
1

The soft link is still needed when using MacPorts. – lenborje Oct 12 '23 at 09:02

score 1 · Answer 3 · answered Feb 19 '19 at 10:27

1

One temporary solution could be:

alias tac='perl -e "print reverse(<>)"'

answered Feb 19 '19 at 10:27

JJoao

12,170
1
23
45

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This just caused me to learn that <> doesn't only read from STDIN, but optionally from @ARGV. https://stackoverflow.com/questions/29020883/less-than-and-greater-than-symbols-together I still don't know if reverse will load the whole file into memory before outputting the lines in reverse order. That would be terrible. – Bruno Bronosky Apr 09 '19 at 18:11
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@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) – JJoao Apr 10 '19 at 07:45

score 0 · Answer 4 · answered Mar 17 '15 at 19:27

0

Install gnu coreutils already compiled with Rudix:

sudo rudix install coreutils

Or download and gui install Rudix coreutils

answered Mar 17 '15 at 19:27

dkmillares

1

How can I get the tac command on OS X?

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