Re: here document and STDIN

[Cai Qian]

The information is helpful. The problem by using

perl -e '
   XXXXX
'

is that there seems no way to using single quota in Perl code any more.

On 5/23/06, Paul Jarc <prj@po.cwru.edu> wrote:
> "Cai Qian" <loricai@gmail.com> wrote:
> > For following code,
> >
> > sh <<EOF
> >       read
> > EOF
> >
> > I have no idea why will not block.
>
> The "read" command reads from the shell's stdin, which is the here
> document.  At the point where the "read" command is executed, the
> shell has already read the "read" command from the here document, so
> the next thing read from there will be end-of-file.  If you want the
> "read" command to read from the original stdin that was present before
> the here document was introduced, you can copy it to another
> descriptor:
>
> sh <<EOF 3<&0
>     read <&3
> EOF
>
> > So I can run some Perl code inside like,
> >
> > perl - <<'EOF'
> >      XXXXX
> >
> > EOF
>
> With perl, it may be easier to use -e instead of a here document:
> perl -e '
>     XXXXX
> '
>
> Then perl will still be connected to the original stdin, without any
> need for duplicating descriptors.
>
>
> paul