grep -P no longer works. How can I rewrite my searches?

It looks like the new version of OSX no longer supports grep -P and as such has made some of my scripts stop working.

var1=`grep -o -P '(?<=<st:italic>).*(?=</italic>)' file.txt`

I need to capture the grep to a variable and I need to use the zero width assertions, as well as \K

var2=`grep -P -o '(property:)\K.*\d+(?=end)' file.txt`

Any alternatives would be greatly appreciated.

If your scripts are for your use only, you can install grep from [homebrew-core][1] using [brew][2]:

brew install grep 

Then it's available as ggrep (GNU grep). [1]: https://github.com/Homebrew/homebrew-core [2]: http://brew.sh/

it doesn't replaces the system grep (you need to put the installed grep before the system one on the PATH).

The version installed by brew includes the -P option, so you don't need to change your scripts.

If you need to use these commands with their normal names, you can add a "gnubin" directory to your PATH from your bashrc like:

PATH="/usr/local/opt/grep/libexec/gnubin:$PATH"

You can export this line on your ~/.bashrc or ~/.zshrc to keep it for new sessions.

Please see here for a discussion of the pro-s and cons of the old --with-default-names option and it's (recent) removal.

If you want to do the minimal amount of work, change

grep -P 'PATTERN' file.txt

to

perl -nle'print if m{PATTERN}' file.txt

and change

grep -o -P 'PATTERN' file.txt

to

perl -nle'print $& while m{PATTERN}g' file.txt

So you get:

var1=`perl -nle'print $& while m{(?<=<st:italic>).*(?=</italic>)}g' file.txt`
var2=`perl -nle'print $& while m{(property:)\K.*\d+(?=end)}g' file.txt`

---

In your specific case, you can achieve simpler code with extra work.

var1=`perl -nle'print for m{<st:italic>(.*)</italic>}g' file.txt`
var2=`perl -nle'print for /property:(.*\d+)end/g' file.txt`

Install ack and use it instead. Ack is a grep replacement written in Perl. It has full support for Perl regular expressions.

OS X tends to provide BSD rather than GNU tools. It does come with egrep however, which is probably all you need to perform regex searches.

example: egrep 'fo+b?r' foobarbaz.txt

A snippet from the OSX grep man page:

use perl;

perl -ne 'print if /regex/' files ...

If you need more grep options (I see you would like -o at least) there are various pgrep implementations floating around the net, many of them in Perl.

If "almost Perl" is good enough, PCRE ships with pcregrep.

There is another alternative: pcregrep.

Pcregrep is a grep with Perl-compatible regular expressions. It has the exactly same usage as grep -P. So it will be compatible with your scripts.

It can be installed with homebrew:

brew install pcre

How about using the '-E' option? It works fine for me, for example, if I want to check for a php_zip, php_xml, php_gd2 extension from php -m I use:

php -m | grep -E '(zip|xml|gd2)'

Equivalent of the accepted answer, but without the requirement of the -P switch, which was not present on both machines I had available.

find . -type f -exec perl -nle 'print $& if m{\r\n}' {} ';' -exec perl -pi -e 's/\r\n/\n/g' {} '+'

This one worked for me:

    awk  -F":" '/PATTERN/' file.txt

Another Perl solution for -P

var1=$( perl -ne 'print $1 if m#<st:italic>([^<]+)</st:italic># ' file.txt)

use the perl one-liner regex by passing the find output with a pipe. I used lookbehind (get src links in html) and lookahead for " and passed the output of curl (html) to it.

bash-3.2# curl stackoverflow.com | perl -0777 -ne '$a=1;while(m/(?<=src\=\")(.*)(?=\")/g){print "Match #".$a." "."$&\n";$a+=1;}'
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  239k  100  239k    0     0  1911k      0 --:--:-- --:--:-- --:--:-- 1919k
Match #1 //ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js
Match #2 //cdn.sstatic.net/Js/stub.en.js?v=fb6157e02696
Match #3 https://ssum-sec.casalemedia.com/usermatch?s=183712&amp;cb=https%3A%2F%2Fengine.adzerk.net%2Fudb%2F22%2Fsync%2Fi.gif%3FpartnerId%3D1%26userId%3D
Match #4 //i.stack.imgur.com/817gJ.png" height="16" width="18" alt="" class="sponsor-tag-img">elasticsearch</a> <a href="/questions/tagged/elasticsearch-2.0" class="post-tag" title="show questions tagged &#39;elasticsearch-2.0&#39;" rel="tag">elasticsearch-2.0</a> <a href="/questions/tagged/elasticsearch-dsl" class="post-tag" title="show questions tagged &#39;elasticsearch-dsl&#39;" rel="tag
Match #5 //i.stack.imgur.com/817gJ.png" height="16" width="18" alt="" class="sponsor-tag-img">elasticsearch</a> <a href="/questions/tagged/sharding" class="post-tag" title="show questions tagged &#39;sharding&#39;" rel="tag">sharding</a> <a href="/questions/tagged/master" class="post-tag" title="show questions tagged &#39;master&#39;" rel="tag
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Match #10 http://pixel.quantserve.com/pixel/p-c1rF4kxgLUzNc.gif" alt="" class="dno
bash-3.2# date
Mon Oct 24 20:57:11 EDT 2016

I had this same problem with grep suddenly on a docker rebuilt, I found the solution here : https://github.com/firehol/firehol/issues/325

just replaced -oP with -oE

echo $some_var | grep -oE '\b[0-9a-f]{5,40}\b' | head -1

Some more options, these also set correct exit status:

• equivalent to 'grep -P "PATTERN" ' :

  cat FILE | perl -e'while(<>){if( (m!PATTERN!) ){$ok++;print}};if(!($ok)){exit 1}'

• equivalent to 'grep -P -i "PATTERN" ' :

  cat FILE | perl -e'while(<>){if( (m!PATTERN!i) ){$ok++;print}};if(!($ok)){exit 1}'

• equivalent to 'grep -v -P "PATTERN" ' :

  cat FILE | perl -e'while(<>){if( !(m!PATTERN!) ){$ok++;print}};if(!($ok)){exit 1}'

For a more cleaner solution use this gist - implemented switches are: -A , -B , -v , -P , -i : https://gist.github.com/torson/bd6931bda0035c4884b2a8c4c64a33b2