WG15 Defect Report Ref: 9945-2-137
Topic: ex ex

This is an approved interpretation of 9945-2:1993.


Last update: 1997-05-20



	Topic:                  ex
	Relevant Sections:

Defect Report:
	From: Mike Convey (mike@novell.co.uk)
	Date: Wed Aug 16 16:40:18 BST 1995

This is an interpretation request for 9945-2:1993.

	Topic: ex
	Section: ("Regular Expressions")

Section says:

1785 The ex utility shall support the BREs described in 2.8.3.  A null BRE
     (//) shall be
1786 equivalent to the last BRE encountered.

Historically, however, ex/vi regular expressions have differed from the
BRE's described in .8.3 in one respect - they accepted backslash as quoting
the following characters within brackets: \, -, ^, and ].

Therefore, the pattern [\^abc] would not historically match \, but only
^, a, b or c.

Was it the intention to change ex/vi's regular expressions in this way?

Interpretation response

The standard clearly states the requirements for  BREs in ex
and conforming implementations must conform to this. 

It is true that historical versions of many utilities  had
minor varients in regular expressions, POSIX.2 regularized most of 
these utilities including all of the editors to use the standard 
regular expressions supported by the regular expression standard routines.


Forwarded to Interpretations group: Aug 16 1995
Recirculated for 30 day review: Oct 19 1995
Finalised: Nov 20 1995