I'm writing a scripts that check the TTL of the ping and found the OS.
According the TTL - the script should let me know which OS it is :
Linux/ Windows or Unix (Hash table)

I'm getting an error on the line where I should use the TTL variable -
and take the right value from the hash (%list) :Use of uninitialized
value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
, <HANDLE> line 3.

Any idea ?


#! C:\Perl\bin\perl -w
use strict;
use warnings;

my %list = (60,"linux",61,"linux",62,"linux",63,"linux",64,"linux",
65,"linux",125,"Windows",126,"Windows",127,"Windows",128,"Wi ndows",
250,"Unix",251,"Unix",252,"Unix",253,"Unix",254,"Unix",255," Unix",
256,"Unix",257,"Unix",258,"Unix",259,"Unix",260,"Unix");
my $path = "hosts.txt" ;
my $machine_IP ;
my $cmd ;

# read machines hosts names List from the txt file c:1.txt and take
the TTL data to th e variable: $line
open (MACHINES,$path) or die "Couldn't open file for writing";
while ($machine_IP = <MACHINES>)
{
chomp($machine_IP) ;
my $line ;
$cmd = "ping $machine_IP";
open(HANDLE,"$cmd|");
while ($line = <HANDLE>)
{
if("$line" =~ "TTL=")
{
$line =~ s/.*TTL=//;
print "TTL = $line\n";
print $list{"$line"} ;
# print "Machine $machine_IP is $list{$line}" ;
last; }
}
}
close HANDLE;
close MACHINES;


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Hi Eyal,

On Thursday 20 Jan 2011 15:38:00 Eyal B. wrote:
> I'm writing a scripts that check the TTL of the ping and found the OS.
> According the TTL - the script should let me know which OS it is :
> Linux/ Windows or Unix (Hash table)
>
> I'm getting an error on the line where I should use the TTL variable -
> and take the right value from the hash (%list) :Use of uninitialized
> value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
> , <HANDLE> line 3.
>
> Any idea ?
>

First of all, you should use a CPAN module for Ping (maybe
http://search.cpan.org/dist/Net-Ping/ ). Otherwise, here are some comments on
your code.

>
> #! C:\Perl\bin\perl -w
> use strict;
> use warnings;

You shouldn't specify -w in the sha-bang. "use warnings;" (which you also
have) is better.

>
> my %list = (60,"linux",61,"linux",62,"linux",63,"linux",64,"linux",
> 65,"linux",125,"Windows",126,"Windows",127,"Windows",128,"Wi ndows",
> 250,"Unix",251,"Unix",252,"Unix",253,"Unix",254,"Unix",255," Unix",
> 256,"Unix",257,"Unix",258,"Unix",259,"Unix",260,"Unix");

It's not a list -it's a hash. And you should use the fat comma ("=>"), and use
some indentation.

> my $path = "hosts.txt" ;
> my $machine_IP ;
> my $cmd ;
>

Don't predeclare the variables. Declare them when needed.

> # read machines hosts names List from the txt file c:1.txt and take
> the TTL data to th e variable: $line
> open (MACHINES,$path) or die "Couldn't open file for writing";

Use three args open and don't use bareword file handles.

> while ($machine_IP = <MACHINES>)
> {
> chomp($machine_IP) ;
> my $line ;
> $cmd = "ping $machine_IP";
> open(HANDLE,"$cmd|");

You should use three-args open, lexical filehandles and "or die". Furthermore,
use $cmd is not needed here as you can interpolate directly from $cmd.

> while ($line = <HANDLE>)
> {
> if("$line" =~ "TTL=")

No need for wrapping $line in double quotes here as $line is a string.

> {
> $line =~ s/.*TTL=//;



> print "TTL = $line\n";
> print $list{"$line"} ;

You can do all that in one regex match.

if (my ($ttl) = $line =~ m{TTL=(\d+)})

> # print "Machine $machine_IP is $list{$line}"
;
> last; }
> }
> }
> close HANDLE;
> close MACHINES;

For more information see:

http://perl-begin.org/tutorials/bad-elements/

Regards,

Shlomi Fish

--
------------------------------------------------------------ -----
Shlomi Fish http://www.shlomifish.org/
Escape from GNU Autohell - http://www.shlomifish.org/open-
source/anti/autohell/

Chuck Norris can make the statement "This statement is false" a true one.

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On 20 January 2011 15:38, Eyal B. <ewinstock [at] gmail.com> wrote:
> I'm writing a scripts that check the TTL of the ping and found the OS.
> According the TTL - the script should let me know which OS it is :
> Linux/ Windows or Unix (Hash table)
>
> I'm getting an error on the line where I should use the TTL variable -
> and take the right value from the hash (%list) :Use of uninitialized
> value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
> , <HANDLE> line 3.
>
> Any idea ?
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if("$line" =3D~ "TTL=3D")
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0{
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0$line =3D~=
s/.*TTL=3D//;
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0print "TTL=
=3D $line\n";
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0print $lis=
t{"$line"} ;
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0# print "M=
achine $machine_IP is $list{$line}" ;
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0last; =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }

Assuming a specific line is made of nothing but TTL=3D, then $line =3D~
s/.*TTL=3D//; will erase the line, leaving you with an empty
(uninitialized) $line variable.

A way to debug this will be to include a print $line just before the
substitution, so you could find what is happening in each stage of the
iteration.

--
Erez

La perfection soit atteinte non quand il n'ya plus rien =E0 ajouter,
mais quand il n'ya plus rien =E0 retrancher.

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Hi Eyal,

I should note that your plain text message is mal-formatted. It's not clear=

which parts were said by me, and which parts were said by you. Next time,
please configure your mailer (GMail.com?) to format the message as plaintex=
t
and to use proper "> " quoting as needed by netiquette rules.

On Friday 21 Jan 2011 10:00:06 =D7=90=D7=99=D7=99=D7=9C =D7=91. wrote:
> Hi Shlomi
> I tried to put this answer on the Google group, but didn't succeed. (Sent
> it but it didn't published)

It's not a Google group - it's a [at] perl.org-hosted mailing list. I don't kno=
w
why it wasn't published, but you can try E-mail postmaster [at] perl.org about i=
t.
I'm CCing the list in any case.

> I hope this is OK I'm sending it right here.

I guess. I'm CCing the list.

> BTW, I read your story and very likes that. It's good and very brave to
> share your self with others.

Which story?

> Looks like you are really dealing with your life.
>
> Back to Perl :
> Tried to implement your recommendations .... step by step .....
>
> #! C:\Perl\bin\perl
> use strict;
> use warnings;
>
> my %list =3D
> (60=3D>"linux",61=3D>"linux",62=3D>"linux",63=3D>"linux",64= 3D>"linux",65=
=3D>"linux",12
> 5=3D>"Windows",126=3D>"Windows",127=3D>"Windows",128=3D>"Win dows",250=3D>=
"Unix",251=3D>
> "Unix",252=3D>"Unix",253=3D>"Unix",254=3D>"Unix",255=3D>"Uni x",
> 256=3D>"Unix",257=3D>"Unix",258=3D>"Unix",259=3D>"Unix",260= 3D>"Unix");

Like I said you should reformat that. And since you have a lot of duplicacy=

you can use something like:

my %ttls_to_os =3D
(
Linux =3D> [60..65],
Windows =3D> [125 .. 128],
Unix =3D> [250 .. 260],
);

And then construct a TTL->OS mapping using
http://perldoc.perl.org/functions/map.html .

>
> my $path =3D "hosts.txt" ;
> # open (MACHINES,$path) or die "Couldn't open file for writing";
> open my $input_fh, "<", $path
> or die "Could not open '$path' - $!";
>
> # Shlomi, you wrote : "Use three args open and don't use bareword file
> handles..."
>
> # I'm asking : Trying to implement that (Though, didn't understand what is
> "bareword")....where do I indicate the MACHINES handle ?

A bareword is something like =C2=ABMACHINES=C2=BB, i.e: starting with an up=
percase
letter and without a "$" sigil in front. And you can do:

[code]
open my $machines_fh, '<', $path
or die "Could not open '$path' - $!";
[/code]

And then use the =C2=AB$machines_fh=C2=BB file handle instead of =C2=ABMACH=
INES=C2=BB.

>
> my $machine_IP ;
> while ($machine_IP =3D <MACHINES>)
> {

This should be written as:

[code]
while (my $machine_ip =3D <$machines_fh>)
[/code]

> chomp($machine_IP) ;
> my $line ;
> my $cmd ;
> $cmd =3D "ping $machine_IP";
> open(HANDLE,"$cmd|");
>
> # Shlomi, you wrote : You should use three-args open, lexical filehandles
> and "or die".
> # I'm asking : Can you pls show me how should I write that ?

You can do:

[code]
open my $handle, "ping $machine_IP|"
or die "Could not open the ping process - $!";
[/code]

In this case, a three args open using '-|' won't work because it's not
implemented in Windows yet.

> # Furthermore, use $cmd is not needed here as you can interpolate directly
> from $cmd.
> # I didn't understand what that means.

See above.

>
> while ($line =3D <HANDLE>)
> {
> if("$line" =3D~ "TTL=3D")
>
> # No need for wrapping $line in double quotes here as $line is a string.
> # as mentioned above




>
>
> {
> $line =3D~ s/.*TTL=3D//;
> print "TTL =3D $line\n";
> print $list{$line} ;
> last; }
> # You can do all that in one regex match.
> # I didn't reach so far ... Is that
>
> # if (my ($ttl) =3D $line =3D~ m{TTL=3D(\d+)})
>

Yes, it's that.

> # print "Machine $machine_IP is $list{$line}" ;
>
>
> }
> }
> close HANDLE;
> close MACHINES;
>
> # Without make the changes about the File Handle -
> I still got the error : Use of uninitialized value within %list in print =
at
> C:\system\Perl\OS-recognize\os-rec5.1_.pl line 35, <HANDLE> line 4.
>

Maybe you have a missing TTL from your hash. Try using a debugger:

http://perl-begin.org/topics/debugging/

Regards,

Shlomi Fish

=2D-
=2D--------------------------------------------------------- -------
Shlomi Fish http://www.shlomifish.org/
Apple Inc. is Evil - http://www.shlomifish.org/open-source/anti/apple/

Chuck Norris can make the statement "This statement is false" a true one.

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Tried to implement your recommendations .... step by step .....

#! C:\Perl\bin\perl
use strict;
use warnings;

my %list = (60=>"linux",61=>"linux",62=>"linux",63=>"linux",
64=>"linux",65=>"linux",125=>"Windows",126=>"Windows",127=>" Windows",
128=>"Windows",250=>"Unix",251=>"Unix",252=>"Unix",253=>"Uni x",
254=>"Unix",255=>"Unix", 256=>"Unix",257=>"Unix",258=>"Unix",
259=>"Unix",260=>"Unix");

my $path = "hosts.txt" ;
# open (MACHINES,$path) or die "Couldn't open file for writing";
open my $input_fh, "<", $path
or die "Could not open '$path' - $!";

# Shlomi, you wrote : "Use three args open and don't use bareword file
handles..."

# I'm asking : Trying to implement that (Though, didn't understand
what is "bareword")....where do I indicate the MACHINES handle ?

my $machine_IP ;
while ($machine_IP = <MACHINES>)
{
chomp($machine_IP) ;
my $line ;
my $cmd ;
$cmd = "ping $machine_IP";
open(HANDLE,"$cmd|");

# Shlomi, you wrote : You should use three-args open, lexical
filehandles and "or die".
# I'm asking : Can you pls show me how should I write that ?
# Furthermore, use $cmd is not needed here as you can interpolate
directly from $cmd.
# I didn't understand what that means.

while ($line = <HANDLE>)
{
if("$line" =~ "TTL=")

# No need for wrapping $line in double quotes here as $line is a
string.
# as mentioned above


{
$line =~ s/.*TTL=//;
print "TTL = $line\n";
print $list{$line} ;
last; }
# You can do all that in one regex match.
# I didn't reach so far ... Is that

# if (my ($ttl) = $line =~ m{TTL=(\d+)})

# print "Machine $machine_IP is
$list{$line}" ;


}
}
close HANDLE;
close MACHINES;

# Without make the changes about the File Handle -
I still got the error : Use of uninitialized value within %list in
print at C:\system\Perl\OS-recognize\os-rec5.1_.pl line 35, <HANDLE>
line 4.

Thanks, Shlomi,

Eyal.


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On Jan 21, 7:50=A0am, moonb... [at] gmail.com (Erez Schatz) wrote:
> On 20 January 2011 15:38, Eyal B. <ewinst... [at] gmail.com> wrote:
>
>
>
> > I'm writing a scripts that check the TTL of the ping and found the OS.
> > According the TTL - the script should let me know which OS it is :
> > Linux/ Windows or Unix (Hash table)
>
> > I'm getting an error on the line where I should use the TTL variable -
> > and take the right value from the hash (%list) :Use of uninitialized
> > value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
> > , <HANDLE> line 3.
>
> > Any idea ?
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if("$line" =3D~ "TTL=3D"=
)
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0{
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0$line =
=3D~ s/.*TTL=3D//;
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0print "T=
TL =3D $line\n";
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0print $l=
ist{"$line"} ;
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0# print =
"Machine $machine_IP is $list{$line}" ;
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0last; =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
>
> Assuming a specific line is made of nothing but TTL=3D, then $line =3D~
> s/.*TTL=3D//; will erase the line, leaving you with an empty
> (uninitialized) $line variable.
>
> A way to debug this will be to include a print $line just before the
> substitution, so you could find what is happening in each stage of the
> iteration.
>
> --
> Erez
>
> La perfection soit atteinte non quand il n'ya plus rien =E0 ajouter,
> mais quand il n'ya plus rien =E0 retrancher.

Hi Erez
print "TTL =3D $line\n"; Does give me the right value ! (I.e TTL =3D 125)
Also print $list{125} ; return the right value
But this is not working : print $list{$line} ;
What can happen for the variable ?


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On 21/01/2011 05:50, Erez Schatz wrote:
> On 20 January 2011 15:38, Eyal B.<ewinstock [at] gmail.com> wrote:
>>
>> I'm getting an error on the line where I should use the TTL variable -
>> and take the right value from the hash (%list) :Use of uninitialized
>> value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
>> ,<HANDLE> line 3.
>>
>> Any idea ?
>> if("$line" =~ "TTL=")
>> {
>> $line =~ s/.*TTL=//;
>> print "TTL = $line\n";
>> print $list{"$line"} ;
>> # print "Machine $machine_IP is $list{$line}" ;
>> last; }
>
> Assuming a specific line is made of nothing but TTL=, then $line =~
> s/.*TTL=//; will erase the line, leaving you with an empty
> (uninitialized) $line variable.

No it won't, it will leave $line containing a null (zero-length) string.
There is no way to change a string value to uninitialized (undef) by
deleting characters from it.

- Rob

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On Jan 21, 4:30=A0pm, rob.di... [at] gmx.com (Rob Dixon) wrote:
> On 21/01/2011 05:50, Erez Schatz wrote:
>
>
>
> > On 20 January 2011 15:38, Eyal B.<ewinst... [at] gmail.com> =A0wrote:
>
> >> I'm getting an error on the line where I should use the TTL variable -
> >> and take the right value from the hash (%list) :Use of uninitialized
> >> value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
> >> ,<HANDLE> =A0line 3.
>
> >> Any idea ?
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if("$line" =3D~ "TTL=
=3D")
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 {
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 $line =
=3D~ s/.*TTL=3D//;
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 print =
"TTL =3D $line\n";
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 print =
$list{"$line"} ;
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 # prin=
t "Machine $machine_IP is $list{$line}" ;
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 last; =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
>
> > Assuming a specific line is made of nothing but TTL=3D, then $line =3D~
> > s/.*TTL=3D//; will erase the line, leaving you with an empty
> > (uninitialized) $line variable.
>
> No it won't, it will leave $line containing a null (zero-length) string.
> There is no way to change a string value to uninitialized (undef) by
> deleting characters from it.
>
> - Rob

ok. So why on print "TTL =3D $line\n"; I do get TTL =3D 125, if it's
undefined ?
Thanks, Rob, for your answer.....


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Hi Eyal,

On Friday 21 Jan 2011 15:55:58 =D7=90=D7=99=D7=99=D7=9C =D7=91. wrote:
> Hi Shlomi, Again.
> I'm sorry for keep sending you mails (It's because my answers to the
> to the group still doesn't work and I sent a complaint to
> postmaster [at] perl.org)
>
> I hope now when I use a plain text message, it will be more understandabl=
e.
> (BTW, now it will use the ">" ? I really not have much experience in
> netiquette rules)

See:

* http://en.wikipedia.org/wiki/Posting_style

* http://www.caliburn.nl/topposting.html

[snipped personal stuff]

> Back to Perl, and to my script.
> Because there are many things to understand, I want to focus on my
> major problem why, following the variable I took from the Regular Ex.:
> $list.
> I don't know why this is working : print $list{125} ;
> But this ain't working : print $list{$line} ; while there is 125 on the
> %line. What can be the difference. (I tried chomp) ?
> I tried to debug, I still can't understand why it's doesn't work !

What does x $line and x \%list say inside the debugger.

>
> (BTW, I understood the bareword issue, and implement it , according to
> your recommendations. Got a new errors :
> Global symbol "$machine_IP" requires explicit package name at
> C:\system\Perl\OS- recognize\os-rec5.01_.pl line 14.
> Global symbol "$machine_IP" requires explicit package name at
> C:\system\Perl\OS- recognize\os-rec5.01_.pl line 15.
> Global symbol "$handle" requires explicit package name at
> C:\system\Perl\OS-reco gnize\os-rec5.01_.pl line 32.

That means you have not declared your variables. Read the thread here:

http://www.nntp.perl.org/group/perl.beginners/2007/07/msg931 72.html

> Execution of C:\system\Perl\OS-recognize\os-rec5.01_.pl aborted due .....
>
> Here is the new code:
>
> [code]
>
> #! C:\Perl\bin\perl
> use strict;
> use warnings;
>
> my %list =3D
> (60=3D>"linux",61=3D>"linux",62=3D>"linux",63=3D>"linux",64= 3D>"linux",65=
=3D>"linux",
> 125=3D>"Windows",126=3D>"Windows",127=3D>"Windows",128=3D>"W indows",
> 250=3D>"Unix",251=3D>"Unix",252=3D>"Unix",253=3D>"Unix",254= 3D>"Unix",255=
=3D>"Unix",
> 256=3D>"Unix",257=3D>"Unix",258=3D>"Unix",259=3D>"Unix",260= 3D>"Unix");
>
> my $path =3D "c:/system/Perl/hosts.txt" ;
> # read an IP List from the txt file c:/system/Perl/BSO2.txt and take
> the TTL data to the variable: $line
> open my $machines_fh, '<', $path
> or die "Could not open '$path' - $!";
> while (my $machine_ip =3D <$machines_fh>) {

Well, the indentation here is wrong, so it's hard to read. This seems like =
an
artefact of an indentation preserving mode while pasting without a special=

reservation for preserving indentation.

Regards,

Shlomi Fish

=2D-
=2D--------------------------------------------------------- -------
Shlomi Fish http://www.shlomifish.org/
Optimising Code for Speed - http://shlom.in/optimise

Chuck Norris can make the statement "This statement is false" a true one.

Please reply to list if it's a mailing list post - http://shlom.in/reply .

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If so, how print "TTL =3D $line\n" does give me the right value ! (I
get TTL =3D 125 if ping to Windows machine.

Thanks, for your answers.

On Jan 21, 4:30=A0pm, rob.di... [at] gmx.com (Rob Dixon) wrote:
> On 21/01/2011 05:50, Erez Schatz wrote:
>
>
>
> > On 20 January 2011 15:38, Eyal B.<ewinst... [at] gmail.com> =A0wrote:
>
> >> I'm getting an error on the line where I should use the TTL variable -
> >> and take the right value from the hash (%list) :Use of uninitialized
> >> value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
> >> ,<HANDLE> =A0line 3.
>
> >> Any idea ?
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if("$line" =3D~ "TTL=
=3D")
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 {
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 $line =
=3D~ s/.*TTL=3D//;
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 print =
"TTL =3D $line\n";
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 print =
$list{"$line"} ;
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 # prin=
t "Machine $machine_IP is $list{$line}" ;
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 last; =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
>
> > Assuming a specific line is made of nothing but TTL=3D, then $line =3D~
> > s/.*TTL=3D//; will erase the line, leaving you with an empty
> > (uninitialized) $line variable.
>
> No it won't, it will leave $line containing a null (zero-length) string.
> There is no way to change a string value to uninitialized (undef) by
> deleting characters from it.
>
> - Rob


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Guys
You claim : s/.*TTL=3D//; will erase the line, leaving with an empty
(uninitialized) $line variable.
I want to ask :
If so, how print "TTL =3D $line\n" does give me the right value !
If it will leave $line containing a null (zero-length or undef) string
- how can I print it ?
(I get TTL =3D 125 if ping to Windows machine)


2011/1/21 Abuse Desk <abuse [at] perl.org>:
>
> On Jan 21, 2011, at 2:53, =D7=90=D7=99=D7=99=D7=9C =D7=91. wrote:
>
> Google Groups might not be sending us the mail -- try posting directly to=
the list by emailing beginners [at] perl.org.
>
> =C2=A0- ask
>
>> Hi
>> I'm sending a reply using the : http://groups.google.com/group/perl.begi=
nners/browse_thread/thread/45594cc9ea0ae4b5/0e6e248cab1d1e62 #0e6e248cab1d1e=
62
>>
>> Reply with my questions to the answers I got.
>> But nothing is published.
>>
>>
>> Thanks
>
>

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On Jan 21, 11:42=A0pm, ewinst... [at] gmail.com ("Eyal B.") wrote:
> On Jan 21, 4:30=A0pm, rob.di... [at] gmx.com (Rob Dixon) wrote:
>
>
>
> > On 21/01/2011 05:50, Erez Schatz wrote:
>
> > > On 20 January 2011 15:38, Eyal B.<ewinst... [at] gmail.com> =A0wrote:
>
> > >> I'm getting an error on the line where I should use the TTL variable=
-
> > >> and take the right value from the hash (%list) :Use of uninitialized
> > >> value in print at D:\system\perl\os-rec\os-rec5_.pl line 24
> > >> ,<HANDLE> =A0line 3.
>
> > >> Any idea ?
> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if("$line" =3D~ "TTL=
=3D")
> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 {
> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 $lin=
e =3D~ s/.*TTL=3D//;
> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 prin=
t "TTL =3D $line\n";
> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 prin=
t $list{"$line"} ;
> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 # pr=
int "Machine $machine_IP is $list{$line}" ;
> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 last=
; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
> I found the issue, and resolve it
> This regex clean unnecessary, extra digits: $line =3D~/.*TTL=3D\s*(\S+)\s=
*$/;


> > > Assuming a specific line is made of nothing but TTL=3D, then $line =
=3D~
> > > s/.*TTL=3D//; will erase the line, leaving you with an empty
> > > (uninitialized) $line variable.
>
> > No it won't, it will leave $line containing a null (zero-length) string=
..
> > There is no way to change a string value to uninitialized (undef) by
> > deleting characters from it.
>
> > - Rob
>
> ok. So why on print "TTL =3D $line\n"; I do get TTL =3D 125, if it's
> undefined ?
> Thanks, Rob, for your answer.....


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