sed and Mac OS X differences with to upper, to lower and whole capture control sequences

问题

I am trying to take the last two letters out of a filename which are uppercase and append them to the filename in lowercase. I expeceted the command:

ls | sed -e "s/.*\([A-Z][A-Z]\)$/\0\/\L\1\E/"

to achieve this and on my Ubuntu box it worked fine but on my Mac it simply prints out a 0/LXXE/ where XX are the correct letters from the capture.

What are the Mac sed equivalents of \0, \L and \E?

I've had a look around the web and several people have noticed that Mac OS X sed is different from Ubuntu sed but most threads talk about the -i requirement for a file extension or empty string (which has previously tripped me up).

回答1:

OSX (BSD) sed doesn't support functions \L, \E etc. Install gnu sed on Mac using this option:

brew install gnu-sed

回答2:

awk alternative:

ls | awk '{print $0 tolower(substr($0,length($0)-1,2))}'

来源：https://stackoverflow.com/questions/18298356/sed-and-mac-os-x-differences-with-to-upper-to-lower-and-whole-capture-control-s