Platform Support for GNU Extensions to Basic Regular Expressions
Summary
The article analyzes GNU extensions to basic regular expressions (BRE) like \+ and the historical context across POSIX, GNU, and various OS kernels. It surveys platform support for the extension across FreeBSD, glibc, musl, macOS, NetBSD, OpenBSD, Illumos, Redox OS, Haiku, SerenityOS, and others, concluding that the extension is non-standard but widely yet variably supported. The piece recommends explicitly using extended regex (-E) when extended functionality is required to avoid portability issues.