CentOS - Aug 2006 - perl script part eval help please?

Greetings

Im am not a perl programmer yet I am trying to learn and am debugging
someone elses perl run script for use on a centos production box I have and
I came across this

elif [ -z "${SMTP_CDB:-}" ]

Can someone please shed some light on what this eval means in English
please?

im mainly concerned with the stuff between the two " yet I need all the
help
I can get

what does that say? Im trying to figure out if there is a typo or something
in the script.

I am not a perl programmer yet im sure I will be before I get done with this
exercise in the next coupla weeks

Thanks and kind regards

 - rh

elif is a contraction of else if used to extend if statements

if Foo do x
elif Bar then y
elif dah then z
else ....
etc

I *think* the -z is to see if variable is set or not (ie - unset variables = 0)

the SMTP_CDB looks like a qmail variable, but my guess is the line in question 
is checking to see if SMTP_CDB variable in a qmail config file has been assigned
a value.

HTH

Steve

Email Lists wrote:
> Greetings
> 
> Im am not a perl programmer yet I am trying to learn and am debugging
> someone elses perl run script for use on a centos production box I have and
> I came across this
> 
> elif [ -z "${SMTP_CDB:-}" ]
> 
> Can someone please shed some light on what this eval means in English
> please?
> 
> im mainly concerned with the stuff between the two " yet I need all
the help
> I can get
> 
> what does that say? Im trying to figure out if there is a typo or something
> in the script.
> 
> I am not a perl programmer yet im sure I will be before I get done with
this
> exercise in the next coupla weeks
> 
> Thanks and kind regards
> 
>  - rh
> 
> 
> 
> 
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

Email Lists wrote:
> Greetings
> 
> Im am not a perl programmer yet I am trying to learn and am debugging
> someone elses perl run script for use on a centos production box I have and
> I came across this
> 
> elif [ -z "${SMTP_CDB:-}" ]
That's not perl, that is part of a shell script. 

${SMTP_CDB:-} returns an empty string if the Variable $SMTP_CDB is not
set. See "Parameter Expansion" in the manual page of bash. And
"test -z
$string" returns true, if $string is empty.

Regards,

Ralph
-- 
Ralph Angenendt......ra at br-online.de | .."Text processing has made it
possible
Bayerischer Rundfunk...80300 M?nchen | ....to right-justify any idea, even one
Programmbereich.Bayern 3, Jugend und | .which cannot be justified on any other
Multimedia.........Tl:089.5900.16023 | ..........grounds." -- J. Finnegan,
USC
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