using qx{}

[muzakfetch]

Hi everyone! I am trying to run an external script that provides data from a script. Using the following:

my @radiusdata = qx{ radiusreport -t -l $username[0] -f /var/log/radac
+ct/65.166.140.210/detail } ;

What happens, is the $username gets translated literally. Anyone shed a little light on this?

Thanks, Muzakfetch

[monkfish]

I am not sure what you mean when you say translated literally, but let me try and help...

$username[0] = "bob";
@foo = qx { echo $username[0] };

qx interpolates the string so @foo[0] will get set to 'bob'.

To avoid this you could escape the string:

$username[0] = "bob";
@foo = qx { echo \$username[0] };

This would cause the $username not to be interpolated and it would let the shell decipher a variable called $username when it called the echo.

Hope that helps.

-monkfish (The Fishy Monk)

9/14/01 Edited to clarify and remove incorrect portion of post.

[CheeseLord]

While you are correct in your statements about interpolation, your second system call will not store anything in $foo[0] besides 0 (or, possibly, 256). The difference between system and qx is quite important - the former returns the return value of the code's execution, and the latter will return the output from the code's execution.

Should you desire to keep the string passed to a qx from interpolating, use single quotes as the delimiter, like so:

@foo = qx'echo $HOME';

Which should store "/home/cheesy\n" or something like that in $foo[0]. I hope that helps...

Update: Changed emphasis in a few places.

Update #2: The node I replied to has had its content altered in a way that makes this node make no sense... the original second system call was as follows:

@foo = system('echo $username[0]');

I hope that clears up any confusion.

His Royal Cheeziness

[Rhandom]

You are correct in your statements about system, qx, and the backtick (`) operator. However, there is little syntactical difference between your example with qx'', and qx{}. Both are correct and will return the result of execution. The previous poster, didn't really mention system at all. (Just observing)



#!/usr/bin/perl -w
 
@username = qw(nobody anybody);
 
@foo = qx{ echo $username[0] };
chomp($foo[0]);
print "'$foo[0]'\n";
 
@foo = qx{ echo \$username[0] };
chomp($foo[0]);
print "'$foo[0]'\n";
 
@foo = qx' echo $username[0] ';
chomp($foo[0]);
print "'$foo[0]'\n";

# prints out
#'nobody'
#'[0]'
#'[0]'



my @a=qw(random brilliant braindead); print $a[rand(@a)];