perl issue ..

zedex · #1 (**permalink**) 09-12-2008

hi
one perl issue i have xml file with 2 values and one condition b.w them

Code:

<rule>
     <val1>12</val1>
     <cond>and</cond>
     <val2>13</val2>
</rule>

i read these values in hash in perl code
$one{val1} = 12
$one{cond} = and
$one{val2} = 13
now i want to form query from this
like if val >= val1 and val <= val2 then do something how to do this in code ?

Code:

if ( val >=  $one{val1} $one{cond} val <= $one{val2} )

this throws error how can i write this kind of statement ? i want this for server monitor script.

era · #2 (**permalink**) 09-12-2008

That's a pretty wicked idea, but if you really think you want to do it,

Code:

if (eval "$val => $one{val1} $one{cond} $val <= $one{val2}")

... assuming the "val" in your example is really actually $val

You should realize that with the double quotes, what eval sees is just a string, no variables. Compare: print "$val => $one{val1} $one{cond} $val <= $one{val2}" -- eval will evaluate what the corresponding print prints.

zedex · #3 (**permalink**) 09-12-2008

thanx for reply i think i should explain u whole situation

i have unix server monitor script in which i have many rules which are hard coded so even for slightest change i have to change code so i have created xml file with no of primary conditions , relation bw them like ( and / or ) actual condition and so on ...

i spent entire day on new code architecture but i think i have to go with little hard coding even i thought its pretty wicked idea but thanx for ur reply i learned something new ....

KevinADC · #4 (**permalink**) 09-13-2008

You can use a look up hash that points to subrotuines depending on the operator, an short example:

Code:

%com = (
   and => \&and,
);	

$one{val1} = 9;
$one{cond} = 'and';
$one{val2} = 13;
$val = 10;

if ($com{$one{'cond'}}->($val,$one{'val1'},$one{'val2'})) {
   print "true";
}

sub and {
   my ($v0,$v1,$v2) = @_;
   return(1) if ($v0 >= $v1 && $v0 <= $v2);
   return(0);
}

Note that '=>' is not a comparison operator, it is the comma operator.

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