[nycbug-talk] Follow-up on grep -P
James E Keenan
jkeen at verizon.net
Wed Nov 6 21:33:46 EST 2013
Thanks to Moe Nasser's presentation tonight, I was inspired to
RTFM for grep. In particular: grep -P. I tried this on three different
machines: an older Mac OSX laptop, an older Debian Linux server
(Linode), and a more up-to-date Debian Linux server. I maintain (so to
speak) the first two boxes; professional sysadmins maintain the latter.
On the two machines I maintain, I use whatever 'grep' came with the
machine. And on these two machines, the '-P' option, though documented
in the manpages, did not work, as those greps had not been compiled with
that option.
Darwin: grep (GNU grep) 2.5.1
$ echo "abacus babble b a ba ab cabriolet" | grep -P '(?=a)b'
grep: The -P option is not supported
Linux (mine): $ grep -V
GNU grep 2.5.3
$ echo "abacus babble b a ba ab cabriolet" | grep -P '(?=a)b'
grep: Support for the -P option is not compiled into this
--disable-perl-regexp binary
Linux (not mine): $ grep -V
GNU grep 2.6.3
$ echo "abacus babble b a ba ab cabriolet xenacb" | grep -P --color
'(?<=b)a'
abacus babble b a ba ab cabriolet xenacb
So, your results with 'grep -P' will depend on how the version of grep
you're using was compiled. YMMV.
Thank you very much.
Jim Keenan
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