very weird echo problem

very weird echo problem

[Uli Zappe]

Hi,

excuse me for bothering you again but I have experienced another  
(to me) very strange problem.

I want to log messages of a shell script to both standard output  
and a logfile, and have to do a "date" call before.

If I do something like

   DATE=$(date)
   echo $MESSAGE
   echo $MESSAGE >> $LOGFILE

everything works as expected.

However, as soon as I capsulate this in a shell function:

   log_function()
   {
      DATE=$(date)
      echo $MESSAGE
      echo $MESSAGE >> $LOGFILE
   }

weird things happen.

Assume in my script I have the following function calls:

   log_function TEST1; log_function TEST2
   log_function TEST3; log_function TEST4

then:

A. If I execute the script from a TERMINAL everything is fine
   (messages get printed to the terminal and to the log file)
B. If I execute the script NOT FROM A TERMINAL (but e.g. cron), then
   the script will stop after the first LINE with log_function calls
   (NOT the first log_function!), i.e. it will print
      TEST1
      TEST2
   to the logfile and then STOP EXECUTION of any code following
C. As soon as I COMMENT OUT ANY ONE of the 3 lines of the log
   function (i.e. no date, or one of the two echo's missing)
   everything again will work as expected. (Concerning date, it is
   sufficient to not put it into a variable, i.e. a pure "date" as
   the first line does no harm.)


The workaround I have found is to write the first echo line as

   echo $MESSAGE 1>&1

i.e I redirected stdout to itself...!?! This shouldn't change  
anything, one would expect, but in fact it solves the problem. Now  
everything works, but as hard as I've tried I simply don't  
understand WHY. Am I totally confused or is this a bug? (I have to  
still use zsh 2.5.02, if that matters).

Thanks for any insight!


                Bye
                        Uli

______________________________________________________________________

Uli Zappe               E-Mail: uli@tallowcross.uni-frankfurt.de
                                (NeXTMail,Mime,ASCII) PGP on request
Lorscher Strasse 5      WWW:    -
D-60489 Frankfurt       Fon:    +49 (69) 9784 0007
Germany                 Fax:    +49 (69) 9784 0042

staff member of NEXTTOYOU - the German NEXTSTEP/OPENSTEP magazine
______________________________________________________________________

Re: very weird echo problem

[Peter Stephenson]

Uli Zappe wrote:
>    log_function()
>    {
>       DATE=$(date)
>       echo $MESSAGE
>       echo $MESSAGE >> $LOGFILE
>    }
> 
>    log_function TEST1; log_function TEST2
>    log_function TEST3; log_function TEST4
> 
> B. If I execute the script NOT FROM A TERMINAL (but e.g. cron), then
>    the script will stop after the first LINE with log_function calls
>    (NOT the first log_function!), i.e. it will print
>       TEST1
>       TEST2
>    to the logfile and then STOP EXECUTION of any code following

Hmm, you can't be telling us everything since TEST1 and TEST2 are
passed as positional parameters, which don't get used by log_function.
How does $MESSAGE get set?  Can you produce an actual minimal script
which shows this?

-- 
Peter Stephenson <pws@ifh.de>       Tel: +49 33762 77366
WWW:  http://www.ifh.de/~pws/       Fax: +49 33762 77413
Deutsches Elektronen-Synchrotron --- Institut fuer Hochenergiephysik Zeuthen
DESY-IfH, 15735 Zeuthen, Germany.

Re: very weird echo problem

[Uli Zappe]

Peter Stephenson wrote:

> Hmm, you can't be telling us everything since TEST1 and TEST2
> are passed as positional parameters, which don't get used by
> log_function.  How does $MESSAGE get set?  Can you produce an
> actual minimal script which shows this?

Oops, sorry, I got a bit too schematic ;-)

It must read:

   log_function()
   {
      DATE=$(date)
      echo $1
      echo $1 >> $LOGFILE
   }

   log_function TEST1; log_function TEST2
   log_function TEST3; log_function TEST4

In the actual script, $DATE is included in the second echo (to the  
logfile), but the effects I describe are reproducable also the way  
that I have notated log_function here.


                Bye
                        Uli

______________________________________________________________________

Uli Zappe               E-Mail: uli@tallowcross.uni-frankfurt.de
                                (NeXTMail,Mime,ASCII) PGP on request
Lorscher Strasse 5      WWW:    -
D-60489 Frankfurt       Fon:    +49 (69) 9784 0007
Germany                 Fax:    +49 (69) 9784 0042

staff member of NEXTTOYOU - the German NEXTSTEP/OPENSTEP magazine
______________________________________________________________________

Re: very weird echo problem

[gwing]

[-- Attachment #1: Type: application/pgp, Size: 1486 bytes --]

Re: very weird echo problem

[Uli Zappe]

Geoff Wing wrote:

> Can you produce more of the script?  There isn't enough there to
> determine what the problem is.  I produced no problems from a
> cron job or via other non-tty specific methods either with 2.5.03
> or 3.* Thanks

You got me wrong. This actually IS practically the complete test  
script (well, #!/usr/bin/zsh is missing, and you should replace  
$LOGFILE by a name...) which reproduces the problem on my machine.

Here is the actual one with which I just tested it again:


***********************************************************
#!/usr/bin/zsh

log()
{
DATE=$(date)
echo $1
echo $1 >>/log
}

log TEST; log TEST_SAME_LINE
log TEST_NEXT_LINE
************************************************************

This script will only write

        TEST
        TEST_SAME_LINE

to /log when called by cron. It works fine when called from a shell.




It also works fine if I apply one of the following changes to log():

1.******************************
DATE=$(date)
echo $1 1>&1
echo $1 >>/log

2.******************************
date
echo $1
echo $1 >>/log

3.******************************
DATE=$(date)
echo $1 >>/log




I'm using zsh 2.5.02 under NEXTSTEP 3.3 Intel. (2.5.02 is the  
distribution that is included in NEXTSTEP 3.3).


                Bye
                        Uli

______________________________________________________________________

Uli Zappe               E-Mail: uli@tallowcross.uni-frankfurt.de
                                (NeXTMail,Mime,ASCII) PGP on request
Lorscher Strasse 5      WWW:    -
D-60489 Frankfurt       Fon:    +49 (69) 9784 0007
Germany                 Fax:    +49 (69) 9784 0042

staff member of NEXTTOYOU - the German NEXTSTEP/OPENSTEP magazine
______________________________________________________________________

Re: very weird echo problem

[Wolfgang Hukriede]

Hello, I checked your script under Nextstep3.2 and zsh 3.0.2 with
and without cron, it runs flawless.

Do yourself a favour and upgrade. Even when Nextstep 3.3 came out,
Next should have included zsh 2.5.03 (was the production release
then and less buggy due to my experience) instead of 2.5.02.

There's even a precompiled binary (3.0.2) in the usual channels, if
you don't want to install from the sources, which indeed is quite
easy. "Works like a charm", as they say.

I don't know about the new 3.1 series though.

Greetings, Wolfgang.

--------------------------------------------------------------------
Uli Zappe <uli@tallowcross.uni-frankfurt.de> wrote

> Here is the actual one with which I just tested it again:
>
>
> ***********************************************************
> #!/usr/bin/zsh
>
> log()
> {
> DATE=$(date)
> echo $1
> echo $1 >>/log
> }
>
> log TEST; log TEST_SAME_LINE
> log TEST_NEXT_LINE
> ************************************************************
>
> This script will only write
>
>         TEST
>         TEST_SAME_LINE
>
> to /log when called by cron. It works fine when called from a shell.

...

> I'm using zsh 2.5.02 under NEXTSTEP 3.3 Intel. (2.5.02 is the
> distribution that is included in NEXTSTEP 3.3).

Re: very weird echo problem

[Uli Zappe]

Wolfgang Hukriede <whukriede@ifm.uni-kiel.de> wrote:

> Hello, I checked your script under Nextstep3.2 and zsh 3.0.2 with
> and without cron, it runs flawless.

Aha!! I've tried it myself with zsh 3.02, and it works! So this is  
obviously a bug and I'm not as stupid as I was afraid I am... :-)

> Do yourself a favour and upgrade.

As far as I'm concerned, I'd love to do this, but the script will  
be published for the whole NEXTSTEP community and I can't build on  
something that's not a standard part of NEXTSTEP.

Anyway, thanks to this crazy workaround 1>&1 (can't believe I found  
that one!) it will work...

Thanks a lot!


                Bye
                        Uli

______________________________________________________________________

Uli Zappe               E-Mail: uli@tallowcross.uni-frankfurt.de
                                (NeXTMail,Mime,ASCII) PGP on request
Lorscher Strasse 5      WWW:    -
D-60489 Frankfurt       Fon:    +49 (69) 9784 0007
Germany                 Fax:    +49 (69) 9784 0042

staff member of NEXTTOYOU - the German NEXTSTEP/OPENSTEP magazine
______________________________________________________________________