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Full Discussion: perl : question about defined()
Top Forums Shell Programming and Scripting perl : question about defined() Post 302428258 by durden_tyler on Wednesday 9th of June 2010 09:27:16 AM
Old 06-09-2010
Quote:
Originally Posted by hcclnoodles
...
is there some way of doing a "notdefined" (i appreciate there is no such thing Smilie)

Code:
 if (defined($new) && notdefined($hostname)) {
        print "ERROR: If using --new, you must define a hostname\n"; 
        exit 1;
 }

...
While there is no such operator as notdefined, the Logical Not - not defined would work for your case. That's because not unary operator is the equivalent of the ! operator(except for the precedence).

Code:
$
$ perl -le '$new="x"; if(defined($new) && ! defined($hostname)){print "ERROR: If using --new, you must define a hostname"}'
ERROR: If using --new, you must define a hostname
$
$ perl -le '$new="x"; if(defined($new) && not defined($hostname)){print "ERROR: If using --new, you must define a hostname"}'
ERROR: If using --new, you must define a hostname
$

tyler_durden
 

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LEARN ABOUT OPENSOLARIS

check-hostname

check-hostname(1M)					  System Administration Commands					check-hostname(1M)

NAME

       check-hostname - check if sendmail can determine the system's fully-qualified host name

SYNOPSIS

	/usr/sbin/check-hostname

DESCRIPTION

       The  check-hostname  script  is a migration aid for sendmail(1M). This script tries to determine the local host's fully-qualified host name
       (FQHN) in a manner similar to sendmail(1M). If check-hostname is able to determine the FQHN of the local host, it reports  success.  Other-
       wise, check-hostname reports how to reconfigure the system so that the FQHN can be properly determined.

FILES

       /etc/hosts	     Host name database

       /etc/nsswitch.conf    Name service switch configuration file

       /etc/resolv.conf      Configuration file for name server routines

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWsndmu 		   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       domainname(1M), sendmail(1M), hosts(4), attributes(5)

SunOS 5.11							    8 Mar 2006							check-hostname(1M)
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