Consider the following typescript:
$ freebsd-version 10.0-RELEASE-p5 $ echo ' found' | sed -n '/[[:blank:]]\+/p' $ echo ' found' | grep '[[:blank:]]\+' found When I do this on Arch Linux with GNU sed:
$ echo ' found' | sed -n '/[[:blank:]]\+/p' found $ echo ' found' | grep '[[:blank:]]\+' found Am I doing it wrong? Why doesn't it work on FreeBSD? How to make it work?
With BSD sed you have to turn on ERE's with the E option.
echo ' found' | sed -nE '/[[:blank:]]+/p' tl;dr see fd0's solution
I did look in the man page before asking, but failed to notice the relevant info, since I figured it doesn't differ significantly from that of Linuxes. But,
$ man sed ... -E Interpret regular expressions as extended (modern) regular expressions rather than basic regular expressions (BRE's). The re_format(7) manual page fully describes both formats. $ man re_format ... Obsolete (“basic”) regular expressions differ in several respects. ‘|’ is an ordinary character and there is no equivalent for its functional‐ ity. ‘+’ and ‘?’ are ordinary characters, and their functionality can be expressed using bounds (‘{1,}’ or ‘{0,1}’ respectively). Also note that ‘x+’ in modern REs is equivalent to ‘xx*’. The delimiters for bounds are ‘\{’ and ‘\}’, with ‘{’ and ‘}’ by themselves ordinary characters. And I did try to use {1,}, I just forgot to escape curly brackets. So surely fd0's solution is generally the best way possible. But others would be:
$ echo ' found' | sed -n '/[[:blank:]]\{1,\}/p' found $ echo ' found' | sed -n '/[[:blank:]][[:blank:]]*/p' found However, not sure what they meant by
Also note that ‘x+’ in modern REs is equivalent to ‘xx*’
Meaning, what it was like in nonmodern ones.
Also, grep's manpage didn't mention re_format entry, which apparently means it has its own implementation of regular expressions. For that matter, it was GNU grep, as opposed to sed.
