On Tue, 11 Feb 2003 20:11:46 -0500, Wiggins D'Anconia wrote:
In addition to Wiggins ...
> foreach my $x (1 .. 255) {
>
>> $a = `ping -q -c 1 192.168.1.$b`;
^^
Could it be that $x instead of $b was meant ?!
>> $b += 1;
You are simulating the work of the loop, as you let $b increment each loop
and the loop has 255 loops. Forget $b.
BTW, allthough it's possible, it's not a good style to work with variables
$a and $b. They are used in Perl globally, e.g. for sorting. See perldoc
perlvar for details.
>> print "192.168.1.$b ";
>> print $a;
>> $usage="ping.pl [-n]"
>
> Missing semi-colon....
>
>> if ($arg = "-n") {$e = 0}
^
The = is an assignment not a comparator.
To test two variables for numerical equalness use ==,
for string equalness use eq.
In your case, it's of course
if ($arg eq "-n").
See again perldoc perlop for details.
Where does $arg come from.
If you meant the (first) argument passed at the command line,
it would be
$ARGV[0].
>> else {$e = 1}
A shorter (and getting more skilled also more readable) way, to set a
variable to one of two values depending on a condition is the following
idiom:
my $e = ($ARGV[0] eq '-n') ? 0 : 1;
>> if ($e = 1) {
^
Again you meant == instead of =.
But if the only sense of $e is to flag whether the argument is -n or not,
why not write it directly:
if ($ARGV[0] eq '-n') {
>> open (LOG, ">>/perl/pinglog.txt";
>
> Missing parentheses. And you should always check to see if open succeeded:
>
> open(LOG,">>/perl/pinglog.txt") or die "Can't open log for appending: $!";
>
>> print `date`;
Perl can do it also for you:
print scalar localtime;
>> print $a;
>> }
>> else {}
You needn't write the else part if it is empty.
Just leave it izt.
>> }
>>
>
> While not using semi-colons at the end of blocks is syntactically
> correct, IMHO it is a very *bad* habit to get into. As it leads to the
> above.
>
> Couple other things,
>
> 1. Name your variables something useful, you have x, b, a, e, and arg,
> all of which tell yourself and future readers nothing about what they
> are doing.
>
> 2. Theoretically your script could open and close the same file to
> append to 255 times, you should check to see if you need to open the log
> before the foreach. Then print to the log if need be during the foreach,
> but don't reopen it, especially since you aren't closing it, which
> brings us to.
>
> 3. Remember to close your open files when you are done with them.
>
> Are you in a learning mode, or writing production code?
Best Wishes,
Janek
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