I'm trying to use a regexp in less to find improperly formatted lines, but the ones I use with grep aren't working, I get an invalid pattern error. The manpage says:
/pattern Search forward in the file for the N-th line containing the pattern. N defaults to 1. The pattern is a regular expression, as recognized by the regular expression library supplied by your system. The search starts at the first line displayed (but see the -a and -j options, which change this).
How do I determine the regexp library supplied by system?
There are a pile of configuration macros defined HAVE_GNU_REGEX, HAVE_POSIX_REGCOMP, HAVE_PCRE2, HAVE_PCRE, HAVE_RE_COMP, HAVE_REGCMP, HAVE_V8_REGCOMP, and it uses different code according to its idea of which of those is the best available at build time
i don't think so. unless someone says that they're using some bizarre palaeo-unix with a primitive regex library, it's reasonable to assume they're using something vaguely modernish. (and, in many cases, it's reasonable to assume they're using gnu/linux unless they state otherwise)
so, except in some very rare and/or unusual environments - mostly archaic, proprietary *nixes (which probably don't even have less installed by default), less uses ERE.
The priority order seems to be POSIX regcomp, pcre2, gnu, regcmp, V8 regcomp, a local V8 regcomp, then re_comp but only if you ask for it, then none. But POSIX regcomp is just back to "library supplied by your system"
It always tries to use ERE, but that isn't an answer to what the library actually is
You're overwhelmingly likely to be in the first case unless the distribution maintainer has Views
@terdon I didn't realize the answer to such a question would be so...undefined. Figured it'd be an "oh yea, it's always this" or a "check this environment variable"...should have learned by now that simple answers aren't common...
I was attempting to use the following regexp in less yesterday:
^\+1[[:space:]]*$, which worked for me in grep. This didn't work in less, so I checked the manpage to see what it does support, and found this:
/pattern
Search forward in the file for the N-th line containing the pattern. N defa...
@Ungeheuer I think that less uses what C makes available on that particular platform. It could choose to use a custom regex library, but that would be an unusual choice.
A swarm manager nodes handles cluster management tasks such as:
1) Maintaining cluster state
2) Scheduling services
3) Serving swarm mode HTTP API endpoints
You may execute any of the - docker swarm - docker node - docker service commands from any of the manager nodes
Applications are r...
@john I rejected your edit here because I thought you were only changing the for to forward which would completely change the meaning, but I hadn't realized you were fixing the format as well! I also failed to see that the original was pretty unclear in the first place. Anyway, sorry! I should have accepted the edit and improved it. My bad :/
I was attempting to use the following regexp in less yesterday:
^\+1[[:space:]]*$, which worked for me in grep. This didn't work in less, so I checked the manpage to see what it does support, and found this:
/pattern
Search forward in the file for the N-th line containing the pattern. N defa...
A swarm manager nodes handles cluster management tasks such as:
1) Maintaining cluster state
2) Scheduling services
3) Serving swarm mode HTTP API endpoints
You may execute any of the - docker swarm - docker node - docker service commands from any of the manager nodes
Applications are r...
