Executing unix commands from a Perl file

carlosAlberto · Jan 22, 2003

Hello,

I would like to execute the following unix command from my Perl file:

snmpwalk -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid

and then display the result to the screen.

How is is possible to execute this command and display the result???????????????

All help greatly appreciated.

Regards,
Carl.

MikeLacey · Jan 22, 2003

a couple of different ways

easy:

$a = `your_command`;
print $a;

but not what you'd call flexible....

a bit harder:

open(CMD, "your_command|&quot

;
while(<CMD>){
print $_;
}

that way you can control how many lines you dislay, edit the content and format of the lines etc Mike

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marblecat · Jan 22, 2003

system("your_command&quot

;

carlosAlberto · Jan 29, 2003

Hi,

I've took the above command a little further but have come up with another error i can't solve.

PROBLEM:
open(RESULTS, "$snmpCommand -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid | &quot

;

The command works when it begins without a variable:
open(RESULTS, "snmpwalk -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid | &quot

;

I have checked to make sure $snmpCommand contains the value 'snmpwalk' but i still get an error.

I am soooo puzzled.... please help!!

Carl.

carlosAlberto · Jan 29, 2003

oh

I define the variable as follows, just in case

my ($snmpCommand) = snmpwalk;

MikeLacey · Jan 29, 2003

Should, I think, be:

my ($snmpCommand) = 'snmpwalk'; Mike

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carlosAlberto · Jan 29, 2003

Hi Mike,

Thanks for the reply.

I tried that and that doesn't seem to work.

I also tried creating a variable as:

my $command = '$snmpCommand -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid | ';

open (RESULTS, $command);

which also didn't work.

????

Carl.

rosenk · Jan 29, 2003

[tt]my $command = '$snmpCommand ...'[/tt]
wouldn't work. Variables don't expand in single quotes.

Try double quotes.

carlosAlberto · Jan 29, 2003

Hi,

I tried the previous comment with no success. Here are my commands:

my $snmpCommand = 'snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |';

open (RESULTS, $snmpCommand)

rosenk · Jan 29, 2003

Was that a typo, or still using single quotes? Your assignment should be:

[tt]my $snmpCommand = "snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |";[/tt]

icrf · Jan 29, 2003

what rosenk is saying:

Code:

my $var1 = &quot;Perl&quot;;
my $var2 = '$var1';
my $var3 = &quot;$var1&quot;;

print &quot;$var1\n$var2\n$var3\n&quot;;

outputs

Code:

Perl
$var1
Perl

When variables are within single quotes, they aren't interpolated (expanded out to their value), but within double quotes, they are. ----------------------------------------------------------------------------------
...but I'm just a C man trying to see the light

carlosAlberto · Jan 29, 2003

yes sorry, I've actually tried both ways.

I'll just include the lines i'm having problems with again:

my $snmpCommand = "snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |";

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Executing unix commands from a Perl file
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carlosAlberto (IS/IT--Manageme) Jan 22, 2003
Hello,

I would like to execute the following unix command from my Perl file:

snmpwalk -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid

and then display the result to the screen.

How is is possible to execute this command and display the result???????????????

All help greatly appreciated.

Regards,
Carl.

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area for this forum!

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MikeLacey (MIS) Jan 22, 2003
a couple of different ways

easy:

$a = `your_command`;
print $a;

but not what you'd call flexible....

a bit harder:

open(CMD, "your_command|&quot

;
while(<CMD>){
print $_;
}

that way you can control how many lines you dislay, edit the content and format of the lines etc
Mike

Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

It's like this; even samurai have teddy bears, and even teddy bears get drunk.

Mark this post as a helpful/expert post!

Inappropriate post?
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area for this forum!

marblecat (Programmer) Jan 23, 2003
system("your_command&quot

;

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area for this forum!

carlosAlberto (IS/IT--Manageme) Jan 29, 2003
Hi,

I've took the above command a little further but have come up with another error i can't solve.

PROBLEM:
open(RESULTS, "$snmpCommand -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid | &quot

;

The command works when it begins without a variable:
open(RESULTS, "snmpwalk -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid | &quot

;

I have checked to make sure $snmpCommand contains the value 'snmpwalk' but i still get an error.

I am soooo puzzled.... please help!!

Carl.

Inappropriate post?
If so, Red Flag it!

Check out the FAQ
area for this forum!

carlosAlberto (IS/IT--Manageme) Jan 29, 2003
oh

I define the variable as follows, just in case

my ($snmpCommand) = snmpwalk;

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If so, Red Flag it!

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area for this forum!

MikeLacey (MIS) Jan 29, 2003
Should, I think, be:

my ($snmpCommand) = 'snmpwalk';
Mike

Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

It's like this; even samurai have teddy bears, and even teddy bears get drunk.

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Inappropriate post?
If so, Red Flag it!

Check out the FAQ
area for this forum!

carlosAlberto (IS/IT--Manageme) Jan 29, 2003
Hi Mike,

Thanks for the reply.

I tried that and that doesn't seem to work.

I also tried creating a variable as:

my $command = '$snmpCommand -v 3 -u testUser -l noAuthNoPriv $ipAddress $miboid | ';

open (RESULTS, $command);

which also didn't work.

????

Carl.

Inappropriate post?
If so, Red Flag it!

Check out the FAQ
area for this forum!

rosenk (Programmer) Jan 29, 2003
my $command = '$snmpCommand ...'
wouldn't work. Variables don't expand in single quotes.

Try double quotes.

Mark this post as a helpful/expert post!

Inappropriate post?
If so, Red Flag it!

Check out the FAQ
area for this forum!

carlosAlberto (IS/IT--Manageme) Jan 29, 2003
Hi,

I tried the previous comment with no success. Here are my commands:

my $snmpCommand = "snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |";

open (RESULTS, $snmpCommand);

@replyData = <RESULTS>;

To which @replyData is empty.

The following command did work:
open (RESULTS, "snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |";

But to bring flexibility there is more than 1 type of snmp command.

Thanks for your help.

Carl.

carlosAlberto · Jan 29, 2003

ooooops, not sure what happened there....

yes sorry, I've actually tried both ways.

I'll just include the lines i'm having problems with again:

my $snmpCommand = "snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |";

open (RESULTS, $snmpCommand);

@replyData = <RESULTS>;

To which @replyData is empty.

The following command did work:
open (RESULTS, "snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |";

But to bring flexibility there is more than 1 type of snmp command.

Thanks for your help.

Carl.

rosenk · Jan 29, 2003

Very strange. This test works perfectly fine for me:
[tt]my $command = "ls |";
open(RESULTS, "$command&quot

;
print while (<RESULTS>);[/tt]

I don't think it will help me know why it's not working, but what version of perl are you using and under what OS?

carlosAlberto · Jan 29, 2003

Perl v5.6.1

Redhat 7.3

justice41 · Jan 29, 2003

This may seem obvious, but is the assignment to $snmpCommand

Code:

my $snmpCommand = &quot;snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |&quot;;

being made after the other variables ($userName, $authPass, etc.) have valid values assigned to them?

Also, are you running this with warnings and strict turned on? (i.e. [tt]use warnings; use strict;[/tt])

jaa

carlosAlberto · Jan 29, 2003

Jaa,

Yep, the other variables are assigned first.

I don't have any warning declarations... Is there 1 of the 2 i should be using do you think????

Thanks.

Carl.

carlosAlberto · Jan 29, 2003

I'm actually 'printing' the $snmpCommand variable which is exactly correct. I have copied it straight to the command line and ran fine.

But for some reason the open () is dieing.......

Carl.

carlosAlberto · Jan 29, 2003

I have the following piece of code to assigned the $snmpCommand variable.

if ($miboid =~ /Table$/) {
my $snmpCommand = "snmptable -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass -CB $ipAddress $miboid |";
}
else {
my $snmpCommand = "snmpwalk -v 3 -Os -u $userName -a MD5 -A $authPass -l authPriv -x DES -X $privPass $ipAddress $miboid |";
print "$snmpCommand";
}

print "$snmpCommand";

The print $snmpCommand works fine within the else, but once out of the loop displays nothing. Is something to do with the 'my'. I used this as i wanted it to be local to this subroutine.

This my help to solve the problem.

Thanks.

Carl.

justice41 · Jan 29, 2003

Yes, the my() localizes $snmpCommand to the if block. You need to declare it in the closing scope of the subroutine block instead.

Code:

sub mysub {
   my $snmpCommand; 
   ...
   if ($miboid =~ /Table$/) {
      $snmpCommand = &quot; .. &quot;;
   }
   else {
      $snmpCommand = &quot; .. &quot;;
   }
}

jaa

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