Re: [Help-bash] Understanding read -r

[Bob Proulx]

Dan Douglas wrote:
> Bob Proulx wrote:
> > Peng Yu wrote:
> > > The following example shows that "\" at the line end means line
> > > continuation. Is this wrong? Or I misunderstand the document?
> > 
> > You forgot to quote the EOF part.  See the stackoverflow reference.
> > Therefore the shell interpreted the string contents before 'read'
> > processing.
> > > read -r -d '' VAR <<EOF
> > Add quotes there.
> >   read -r -d '' VAR <<'EOF'
> > Again, this has to do with the here-document part and not the 'read' part.
> 
> This also suppresses the expansions of course. Not sure if you want that.

Of course I was addressing only the specific point that the read had
not been given any backslashes and therefore was not able to read them
verbatim.  The issue of quoting is a separate item.

Of course I wasn't sure why there was a need to 'read' into a variable
at that point.  But didn't open that question.

> { var=$(</dev/stdin); } <<EOF
> blah
> $foo $bar\
> more text
> EOF
> 
> Now both line continuations and expansions are done as you probably
> want them, rather than letting read mangle things without -r.

I personally dislike the use of /dev/stdin and the others because they
are non-portable across kernels and cause me trouble.  It is a
specific kernel feature that across the systems I care about is
definitely not portable.  YMMV.

> As an aside, mksh has an interesting syntax to assign a heredoc
> result directly to a variable:
> 
> # mksh
> 
> var=<<EOF
> ...
> EOF
> 
> This is optimized to happen in memory with no temporary file.

Looks like a nice feature.

Bob