Re: Confusing/unclear documentation of Sed back references

[Eric Blake]

On 11/26/2014 12:29 PM, Bob Proulx wrote:
> 
> The invocation section documents the -r option.
> 
>   https://www.gnu.org/software/sed/manual/sed.html#Invoking-sed
> 
>   -r
>   --regexp-extended
>       Use extended regular expressions rather than basic regular
>       expressions.  Extended regexps are those that egrep accepts;
>       they can be clearer because they usually have less backslashes,
>       but are a GNU extension and hence scripts that use them are not
>       portable.  See [Extended regular expressions].

This is no longer entirely true.  POSIX has proposed standardizing the
-E synonym of -r, which means that it IS portable to use 'sed -E' to get
extended regular expressions in modern sed implementations, and that it
is no longer a GNU-only extension:
http://austingroupbugs.net/view.php?id=528
(However, it is still true that the spelling 'sed -r' is still a GNU
extension, and you should get used to 'sed -E' instead)

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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