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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 REDHAT

drop_operator

DROP 
OPERATOR(7)						   SQL Commands 						  DROP OPERATOR(7)

NAME

       DROP OPERATOR - remove a user-defined operator

SYNOPSIS

       DROP OPERATOR id ( lefttype | NONE , righttype | NONE ) [ CASCADE | RESTRICT ]

   INPUTS
       id     The identifier (optionally schema-qualified) of an existing operator.

       lefttype
	      The type of the operator's left argument; write NONE if the operator has no left argument.

       righttype
	      The type of the operator's right argument; write NONE if the operator has no right argument.

       CASCADE
	      Automatically drop objects that depend on the operator.

       RESTRICT
	      Refuse to drop the operator if there are any dependent objects.  This is the default.

   OUTPUTS
       DROP OPERATOR
	      The message returned if the command is successful.

       ERROR: RemoveOperator: binary operator 'oper' taking 'lefttype' and 'righttype' does not exist
	      This message occurs if the specified binary operator does not exist.

       ERROR: RemoveOperator: left unary operator 'oper' taking 'lefttype' does not exist
	      This message occurs if the left unary operator specified does not exist.

       ERROR: RemoveOperator: right unary operator 'oper' taking 'righttype' does not exist
	      This message occurs if the right unary operator specified does not exist.

DESCRIPTION

       DROP OPERATOR drops an existing operator from the database.  To execute this command you must be the owner of the operator.

       The left or right type of a left or right unary operator, respectively, must be specified as NONE.

   NOTES
       The DROP OPERATOR statement is a PostgreSQL language extension.

       Refer to CREATE OPERATOR [create_operator(7)] for information on how to create operators.

USAGE

       Remove power operator a^n for int4:

       DROP OPERATOR ^ (int4, int4);

       Remove left unary negation operator (! b) for boolean:

       DROP OPERATOR ! (none, bool);

       Remove right unary factorial operator (i !) for int4:

       DROP OPERATOR ! (int4, none);

COMPATIBILITY

   SQL92
       There is no DROP OPERATOR in SQL92.

SQL - Language Statements					    2002-11-22							  DROP OPERATOR(7)
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