Boost: How to use \\+ in C POSIX regex interface

Asked Jul 02 '18 at 13:23

Active Jul 02 '18 at 13:33

Viewed 149 times

I am trying to use BOOST.Regex POSIX Compatible C API's. I am using regcomp() to match an expression like a\+, which should match aa and aaa, while using cflags=REG_BASIC. I have regcomp( reg, "a\\+", REG_BASIC) but it is not working.

I found a link stating that \+ is not part of the POSIX standard. But I found in Boost POSIX Basic regular expression documentation an Emacs variation that supports \+ syntax.

How can I use \+ in POSIX Basic Regular Expressions? Or in other words, enable Emacs variation.

References:

edited Jul 02 '18 at 13:33

Wiktor Stribiżew

607,720
39
448
563

asked Jul 02 '18 at 13:23

Mohamed Elsayed

1

You do not need the `+` quantifier since you may use `\{1,\}`. `\+` is an extension for some POSIX regex implementations (as in GNU sed), and is not portable. – Wiktor Stribiżew Jul 02 '18 at 13:37
Well, if you plan to use `emacs` "flavor", use `boost::regex::emacs` and enjoy `+`. – Wiktor Stribiżew Jul 02 '18 at 13:50
@WiktorStribiżew Actually I am using the POSIX Compatible C API's as the APIs are called from c code. Is there a way to use `boost::regex::emacs` from c code? – Mohamed Elsayed Jul 02 '18 at 15:22
It seems you need `REG_EXTENDED` rather than `REG_BASIC` then. – Wiktor Stribiżew Jul 02 '18 at 16:35

Boost: How to use \\+ in C POSIX regex interface

0 Answers0