HUSH logical AND/OR expressions

= true && false || echo ECHO

Trying to get a better handle of HUSH shell expressions, this does not work as I expect:
=> false && true || echo ECHO
=> false && false || echo ECHO

none prints ECHO, seems like a bug?

This the only one that prints ECHO

Quoted 1 line

= true && false || echo ECHO

Hi Joakim,

Quoted 5 lines · Joakim Tjernlund

Trying to get a better handle of HUSH shell expressions, this does not work as I expect:
=> false && true || echo ECHO
=> false && false || echo ECHO

none prints ECHO, seems like a bug?

I think it works as it should. false followed by && will terminate always.

Quoted 2 lines

This the only one that prints ECHO

Quoted 1 line

= true && false || echo ECHO

This also seems correct. Passing true into && and false into || will always continue.

Dear Joe Hershberger,

Quoted 16 lines · Joe Hershberger

Hi Joakim,

Quoted 7 lines · Joakim Tjernlund

Trying to get a better handle of HUSH shell expressions, this does not work as I expect:
=> false && true || echo ECHO
=> false && false || echo ECHO

none prints ECHO, seems like a bug?

I think it works as it should. false followed by && will terminate always.

Quoted 8 lines

Quoted 3 lines

This the only one that prints ECHO

Quoted 2 lines

= true && false || echo ECHO

This also seems correct. Passing true into && and false into || will always continue.

I thought hush is supposed to be mostly similar to sh. On my Linux desktop, bash (which is supposed to be backward compatible with sh) says

$ which sh
/usr/bin/sh
$ ls -l /usr/bin/sh
lrwxrwxrwx 1 root root 4 Apr 17 14:43 /usr/bin/sh -> bash
$ sh --version
GNU bash, version 4.2.46(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

$ sh
sh-4.2$ false && true || echo ECHO
ECHO
sh-4.2$ false && false || echo ECHO
ECHO
sh-4.2$ true && false || echo ECHO
ECHO
sh-4.2$ exit
exit

Is this one of the places where hush and sh are not the same?

Hi James,

Quoted 13 lines · James Chargin

Dear Joe Hershberger,

Quoted 10 lines · Joe Hershberger

Hi Joakim,

Quoted 5 lines · Joakim Tjernlund

Trying to get a better handle of HUSH shell expressions, this does not work as I expect:
=> false && true || echo ECHO
=> false && false || echo ECHO

I always just assumed this was a limitation of hush, but it's now looking like a bug instead.

I haven't debugged into it, but I tend to stay away from hush these days. When I've submitted a bug fix to this area I've been told that we should upgrade wholesale instead, and I've haven't been up for that task so far. http://lists.denx.de/pipermail/u-boot/2012-November/139841.html

Perhaps there is an easy, minor bugfix for this that would be palette-able.

Dear Joe,

Quoted 21 lines · Joe Hershberger

Hi James,

Quoted 16 lines · James Chargin

Dear Joe Hershberger,

Quoted 12 lines · Joe Hershberger

Hi Joakim,

Quoted 6 lines · Joakim Tjernlund

Trying to get a better handle of HUSH shell expressions, this does not work as I expect:
=> false && true || echo ECHO
=> false && false || echo ECHO

...

Quoted 9 lines

I always just assumed this was a limitation of hush, but it's now looking like a bug instead.

I haven't debugged into it, but I tend to stay away from hush these days. When I've submitted a bug fix to this area I've been told that we should upgrade wholesale instead, and I've haven't been up for that task so far.
http://lists.denx.de/pipermail/u-boot/2012-November/139841.html

That's a great conversation with Wolfgang, thanks for the reference.

Like you, I have tended to use hush carefully. It is similar to sh/bash, but different enough that I never count on an easy port of bash script fragments.

I noticed you asked for a reference to the original hush code that is the origin for U-Boot's adaptation. I couldn't find a reply to that question. I also haven't been able to find anything with a quick we search. Do you know where it did come from?

Quoted 3 lines

Perhaps there is an easy, minor bugfix for this that would be palette-able.

I've been "afraid" of the hush code for a while. I don't think I want to mess with it now. I'll just continue to work with what we've got, carefully.

Thanks again for your attention,

Quoted 5 lines

I noticed you asked for a reference to the original hush code that is the origin for U-Boot's adaptation. I couldn't find a reply to that question. I also haven't been able to find anything with a quick we search. Do you know where it did come from?

I never got a response, but it appears to be busybox...

Dear Joe,

Quoted 7 lines · In message <CANr=Z=YxsT-VOje5jA0k00BSxNROXBOPXMG-Q_8_7jAYN=fJCw@mail.gmail.com>…

Quoted 5 lines

I noticed you asked for a reference to the original hush code that is the origin for U-Boot's adaptation. I couldn't find a reply to that question. I also haven't been able to find anything with a quick we search. Do you know where it did come from?

I never got a response, but it appears to be busybox...

Oops, sorry. Yes, of course it is busybox.

As far as I can tell, it was added around October 2001 to the PPCBoot project as part of the PPCBoot v1.1.0 release:

* Added "hush" shell (from Busybox) as alternative command line interpreter, thus enabling powerful command line syntax like if...then...else...fi conditionals or `&&' and '||' constructs ("shell scripts").

See the README file for information about implementation and usage.