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To: zsh-workers@math.gatech.edu
Subject: PATCH: 3.1.5: eval with exported vars
In-Reply-To: "Phil Pennock"'s message of "Fri, 11 Dec 1998 08:05:58 NFT."
             <19981211080558.46630@athenaeum.demon.co.uk> 
Date: Fri, 11 Dec 1998 10:52:46 +0100
From: Peter Stephenson <pws@ibmth.df.unipi.it>
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Phil Pennock wrote:
> Trying this:
> % FOO=x eval sh -c 'echo $FOO'
> and then without the eval, it seems the eval loses the auto-export
> functionality, in both 3.0.5 and 3.1.5.  It doesn't appear to be
> documented though.

The workaround is

eval 'FOO=x sh -c '\'echo $FOO'\'

by the way.  (Note all the quotes:  see below.)

> Bug?

I was going to say yes, but it's specifically mentioned in the source
that it does this (exec.c, line 1793 of my current version):

	    if (cmd->vars) {
		/* Export this if the command is a shell function,
		 * but not if it's a builtin.
		 */
		addvars(cmd->vars, is_shfunc);

I think the idea must have been that `builtins don't need values
exported' which, as you've seen, is not true in this case.  The patch
is the simplest fix, and I think it's good enough.

There's something that had me horribly confused (though it's actually
working the way God intended):

% FOO=x eval sh -c 'echo $FOO'
<nothing printed>

That's because eval sees the string "sh -c echo $FOO" and turns this
into sh -c 'echo' 'x', so sh gets an 'echo' command with $0 set to x.
To prove it:

% FOO=x eval sh -c '"echo \$0" $FOO'
x

(why $0 not $1?) so you really need

% FOO=x eval sh -c \''echo $FOO'\'
x

phew.

*** Src/exec.c.eval	Thu Dec 10 11:24:46 1998
--- Src/exec.c	Fri Dec 11 10:14:01 1998
***************
*** 1792,1800 ****
  
  	    if (cmd->vars) {
  		/* Export this if the command is a shell function,
! 		 * but not if it's a builtin.
  		 */
! 		addvars(cmd->vars, is_shfunc);
  		if (errflag) {
  		    restore_params(restorelist, removelist);
  		    lastval = 1;
--- 1792,1802 ----
  
  	    if (cmd->vars) {
  		/* Export this if the command is a shell function,
! 		 * but not if it's a builtin, unless the builtin
! 		 * is an eval.
  		 */
! 		addvars(cmd->vars, is_shfunc ||
! 			(is_builtin && ((Builtin)hn)->funcid == BIN_EVAL));
  		if (errflag) {
  		    restore_params(restorelist, removelist);
  		    lastval = 1;



Peter Stephenson <pws@ibmth.df.unipi.it>       Tel: +39 050 844536
WWW:  http://www.ifh.de/~pws/
Dipartimento di Fisica, Via Buonarroti 2, 56127 Pisa, Italy