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From: vincente13 on 11 Jun 2006 23:11
Hi all


Im using
system("ps -fu $USER | grep $INSTANCE | grep -v grep | awk {print $2} "
)

$USER and $INSTANCE are variables from my perl program

However $2 is suppose to be from the pipe output.
Somehow Perl is interpreting $2 to be some variables from the program
itself

So how can differentiate the program variables and system variables?

Appreciate any help

From: vincente13 on 11 Jun 2006 23:34
It seems like i can do this
system("ps -fu $USER | grep $INSTANCE | grep -v grep | awk {print \$2}
")

Put in a backslash

vincente13(a)gmail.com wrote:
> Hi all
>
>
> Im using
> system("ps -fu $USER | grep $INSTANCE | grep -v grep | awk {print $2} "
> )
>
> $USER and $INSTANCE are variables from my perl program
>
> However $2 is suppose to be from the pipe output.
> Somehow Perl is interpreting $2 to be some variables from the program
> itself
>
> So how can differentiate the program variables and system variables?
>
> Appreciate any help

From: J?rgen Exner on 11 Jun 2006 23:50
vincente13(a)gmail.com wrote:
> system("ps -fu $USER | grep $INSTANCE | grep -v grep | awk {print $2}
> " )

Well, the first question would be why are you forking out an external grep
with all the process overhead involved instead of simply using Perl's
buildin grep() command. And the same for awk. There is nothing that awk can
do that Perl can't do.

> $USER and $INSTANCE are variables from my perl program
>
> However $2 is suppose to be from the pipe output.

Actually now. $2 is supposed to be passed literally as a command line
argument to awk without any interpolation whatsoever.

> Somehow Perl is interpreting $2 to be some variables from the program
> itself

Of course. It is the second group that was matched successfully by the most
recent regular expression.

> So how can differentiate the program variables and system variables?

You don't. $2 is not a 'system' variable, whatever that is supposed to mean.
You want to pass the literal text '$2' to awk. And that's simply done by
escaping the $ sign with a backslash.

jue


From: John W. Krahn on 12 Jun 2006 02:01
vincente13(a)gmail.com wrote:
>
> Im using
> system("ps -fu $USER | grep $INSTANCE | grep -v grep | awk {print $2} "
> )
>
> $USER and $INSTANCE are variables from my perl program
>
> However $2 is suppose to be from the pipe output.
> Somehow Perl is interpreting $2 to be some variables from the program
> itself
>
> So how can differentiate the program variables and system variables?

Try it like this instead:

print
map { ( split )[ 1 ], "\n" }
grep /\Q$INSTANCE/,
`ps -fu $USER`;



John
--
use Perl;
program
fulfillment
From: Ted Zlatanov on 12 Jun 2006 15:07
On 11 Jun 2006, vincente13(a)gmail.com wrote:

> It seems like i can do this
> system("ps -fu $USER | grep $INSTANCE | grep -v grep | awk {print \$2}
> ")

Just use sprintf! It's clearer, too.

system sprintf('ps -fu %s | grep %s | grep -v grep | awk {print $2}',
$USER,
$INSTANCE);

Of course, what you are doing is not portable, probably wrong, and
better done with Proc::ProcessTable :)

Ted
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