BusyBox 1.19.3, built against uClibc 0.9.32, on i686 Linux


The Gnu regex extensions \` and \' work properly in busybox grep:

# printf 'abc\ndef' | grep -oz '\`[a-f].' | od -cAn
   a   b  \0

# printf 'abc\ndef' | grep -oz '.[a-f]\'\' | od -cAn
   e   f  \0

So it looks like uClibc is handling them properly. And \' also seems to work right with BusyBox sed:

# printf 'abc\ndef' | sed -n 'N; s/.[a-f]\'\''/=&=/gp'; echo
abc
d=ef=

but there's something wrong with sed's handling of \`:

# printf 'abc\ndef' | sed -n 'N; s/\`[a-f]./=&=/gp'; echo
=ab==c
==de=f

Expected output:
=ab=c
def