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How to backreference named captures in pcreSubstitute

tweeksii

I am able to use numbered backreferences within pcreSubstitute:

> string = "cdsDefTechLib from file internal_implicit"
"cdsDefTechLib from file internal_implicit"
> pcreExecute(pcreCompile("(\\w+) from file (\\w+)") string)
t
> pcreSubstitute("Found \\1 and \\2.")
"Found cdsDefTechLib and internal_implicit."
>

But when I try to use named backreferences, pcreSubstitute doesn't seem to understand them!

> pcreExecute(pcreCompile("(?P<f>\\w+) from file (?P<b>\\w+)")
string)
t
> pcreSubstitute("Found \\k<FOO> and \\k<BAR>")

"Found k<FOO> and k<BAR>"
> pcreSubstitute("Found \\k'FOO' and \\k'BAR'")
"Found k'FOO' and k'BAR'"
> pcreSubstitute("Found \\k{FOO} and \\k{BAR}")
"Found k{FOO} and k{BAR}"
> pcreSubstitute("Found ?P<FOO> and ?P<BAR>")
"Found ?P<FOO> and ?P<BAR>"
> pcreSubstitute("Found \\?P<FOO> and \\?P<BAR>")
"Found ?P<FOO> and ?P<BAR>"
> pcreSubstitute("Found \\(?P=FOO\\)")
"Found (?P=FOO)"
> pcreSubstitute("Found (?P=FOO)")
"Found (?P=FOO)"
> pcreSubstitute("Found (?p=FOO)")
"Found (?p=FOO)"


So, does anybody know how to refer to named backreferences in pcreSubstitute (and pcreReplace)?

  • Tom,

    I think it's probably that we're using too old a version of PCRE (from pcre.org) - it was first added about 12 years ago and it may not have been updated since. I suspect only limited support for named back references was available then (I think it was modelled after Python's syntax then). I can't get it to work either.

    You probably should contact customer support so that we can get PCRE updated (if this is indeed the problem) to use a newer version of the libraries.

    Regards,

    Andrew.

  • in reply to Andrew Beckett

    Hi Andrew,

    Sorry for the late reply--there have been some rather distracting events at my employer recently, but I wanted to be sure to thank you for your detailed answer. 

    After discussing the matter with my colleagues, we decided to hold off on opening a customer support case until we really need to use this feature, as thus far we have been content to use the numbered backreferences (this issue only came up because a contractor asked about it out of curiosity).  It's good to know that the documentation on pcre.org might describe features that are not available (yet) in the version built into Virtuoso!  I wonder if there's a way to directly determine which version is actually in Virtuoso today....

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