Re: problem piping output of shell builtin

[Pavol Juhas <juhas@xxxxxxxxxx>]

On Mon, Jan 05, 2004 at 07:26:15PM +0000, gj@xxxxxxxxxxxxxxxx wrote:
> Hi all,
> 
> I'm migrating from bash to zsh. It hasn't been so bad because I'm sort of new
> to shell programming anyways ( though I did have "fun" figuring out that zsh
> arrays start incrementing from 1 as opposed to bash's 0 :). I thought I'd
> share the latest hiccup...
> 
> Why can't I pipe the output of 'jobs' thusly?

AFAIK, all the shells run one side of the pipe in a subshell.  bash
executes subshell for the right side of the pipe, however zsh does
so for the left side.  Therefore the `jobs' command in 
`jobs|read line' is evaluated in the subshell of zsh, which has no
knowledge about processes in the parent shell - and produces no
output.  Left side subshell is however advantageous in other
situations, just compare

  zsh -c 'echo 10|read a; echo .$a'
  .10
  bash -c 'echo 10|read a; echo .$a' 
  .

To access information in the zsh job table, you need to use the
builtin associate arrays jobtexts, jobstates and jobdirs, for example:

  for j in ${(k)jobstates}; do
    print -- "[$j] ${jobstates[$j]} ${jobtexts[$j]} in ${jobdirs[$j]}"
  done

HTH,

Pavol