sh/bash incompatibility - noticeable with Netscape

sh/bash incompatibility - noticeable with Netscape

[Chris Laas]

Since I started using zsh, I've been getting errors with running helper
apps under Netscape, and I finally investigated the cause.  I have
/bin/sh symbolically linked to zsh (instead of the default bash on
Slackware Linux) and it consistently fails with a parse error whenever
a helper app is run from Netscape.  By linking /bin/sh to /bin/echo, I
discovered that Netscape runs a line of the form:

/bin/sh -c "((helper-app); rm /var/tmp/MO0123456789.foo)&"

where helper-app is the text in the Helpers tab of the General Options
dialog, and the temp file is the downloaded file.

This line runs fine with bash, but zsh parses the leading (( as an
arithmetic expression opening, and fails.  There is no way I can figure
out to convince Netscape to put a space between the two leading
open-parens.

So, what it boils down to is, could we have a fix to the parsing code
to recognize this condition (possibly only when zsh is in
sh-compatibility mode)?

--Chris

-- 
Such has been the patient sufferance of these colonies; and such is
now the necessity which constrains them to alter their former systems
of government.
    -- Thomas Jefferson, Prologue, "Declaration of Independence"
______________________________________________________________________
Chris Laas:  Unix, C++, Perl, Tcl/Tk / mailto:chrisl@cybercom.net
Limit[tech->Inf](words/acronyms)==0 / http://www.cybercom.net/~chrisl/

Re: sh/bash incompatibility - noticeable with Netscape

[Clint Adams]

> This line runs fine with bash, but zsh parses the leading (( as an
> arithmetic expression opening, and fails.  There is no way I can figure
> out to convince Netscape to put a space between the two leading
> open-parens.

This only works with bash 1.x.  bash 2.0 will properly choke in the same way
as zsh.

Better to fix the bug in Netscape (and harass them about fixing it)

This is a slightly modified excerpt of the Debian netscape installer script
(for perl)

undef $/;
open(NETSCAPE,"</tmp/netscape.orig") || die "ERROR: Could not read netscape exec
utable -- $!\n";
$netscape = <NETSCAPE>;
close(NETSCAPE);

$netscape =~ s/\(\(\0cat %s \| \0\);/\( \0cat %s \| \0 ;/;

$outfile='/tmp/netscape.patched';
open(NETSCAPE,">$outfile") || die "ERROR: Could not write '$outfile' -- $!\n";
print NETSCAPE $netscape;
close(NETSCAPE);
chmod 0755,$outfile;

Re: sh/bash incompatibility - noticeable with Netscape

[Chet Ramey]

> > This line runs fine with bash, but zsh parses the leading (( as an
> > arithmetic expression opening, and fails.  There is no way I can figure
> > out to convince Netscape to put a space between the two leading
> > open-parens.
> 
> This only works with bash 1.x.  bash 2.0 will properly choke in the same way
> as zsh.

...and yet bash-2.01 will have a fix.  I fixed the bash parsing code
so that it requires an arithmetic command to begin with `((', end
with `))', and have an equal number of open and close parens.  If it
does not end with `))', it is treated as a nested subshell.  A non-
balancing number of open and close parens is treated as a syntax error.


-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer

Chet Ramey, Case Western Reserve University	Internet: chet@po.CWRU.Edu