bug#19414: bug in sed

[Bob Proulx]

Buchs, Kevin J. wrote:
> I am using sed, version 4.2.1 on a few different systems. What I have
> discovered is that inside a substitute command, a space alone is magically
> anchored at the start of the line in an anti-greedy match.

First, thank you for your bug report.  Efforts to find and fix bugs
are appreciated.  However...

Could you provide a test case *along with the output* that you are
expecting to see?  Otherwise any of us that look are just going to see
what we expect and go, yep, looks okay to me.

> As an example, consider this input stream:
> 
>  a                     <-- leading space
> b c
> d  e
> f    g

Sure.

> Along with these one-liner invocations:
> 
> sed -e 's/ *//'
> sed -e 's/[ ]*//'

Sure.

> sed -e 's/[[:space::]]*//'

Syntax error.  You have two ':' characters where you almost certainly
wanted only one.

> sed -e 's/ ?//'
> sed -e 's/ +//'

Those look like you want extended regular expressions in those two
because of the use of ? and + but you are using the basic regular
expressions by the syntax.  So those probably won't do what you want
but will work correctly.

> What seems to be happening is that the wildcard match gets anchored to the
> beginning of the line with a zero character hit.
> 
> This case seems to apply not only to spaces but other characters.

Please provide the output you are expecting.  This is what I get and
expect:

>  a
> b c
> d  e
> f    g

  sed -e 's/ *//'
  a
  b c
  d  e
  f    g

  sed -e 's/[ ]*//'
  a
  b c
  d  e
  f    g

  sed -e 's/[[:space:]]*//'
  a
  b c
  d  e
  f    g

  sed -e 's/ \?//'
  a
  b c
  d  e
  f    g

  sed -e 's/ \+//'
  a
  bc
  de
  fg

Those are all as expected.  Are you expecting anything different?

Bob