pipe used in perl - as in unix sense

[amanjun]

Hi


I am trying to use "pipe" as in the unix command line sense in Perl
below:



for(`ls $ARGV[0]`)

{

$contents = `ls $_ \| wc \| awk '{print $1}'` ;

print $contents if ($contents != 0) ;

}



Here I am trying to findout the empty directories in $ARGV[0].

It gives errors like:



sh: -c: line 2: syntax error near unexpected token `|w'

sh: -c: line 2: ` |wc'



Can any of you help me in implementing this function?

Thank you.

Manju

 

[Tad McClellan]

I am trying to use "pipe" as in the unix command line sense in Perl
below:



for(`ls $ARGV[0]`)

You shouldn't shell out for things that are easily done in native Perl:

for ( glob $ARGV[0] )

$contents = `ls $_ \| wc \| awk '{print $1}'` ;

^^
^^

Since you want that to be a shell variable (not a Perl variable),
you had better backslash the dollar sign.

You should always enable warnings and strict when developing Perl programs:

use warnings;
use strict;

 

[Brian Wakem]

Hi


I am trying to use "pipe" as in the unix command line sense in Perl
below:



for(`ls $ARGV[0]`)

What happens if $ARGV[0] eq ';rm -rf /' ?

 

[A. Sinan Unur]

Hi


I am trying to use "pipe" as in the unix command line sense in Perl
below:



for(`ls $ARGV[0]`)

What happens if $ARGV[0] eq ';rm -rf /' ?

In addition to the deathly security hole, why would anyone want to spawn
about (3(n+1) + 1), where n is the number of lines ls returns, external
processes for something that can easily be done in Perl?

Sinan

 

[John W. Krahn]

I am trying to use "pipe" as in the unix command line sense in Perl
below:

for(`ls $ARGV[0]`)

That won't work for all file names, better to use opendir/readdir or glob.

perldoc -f opendir
perldoc -f readdir
perldoc -f glob

{
$contents = `ls $_ \| wc \| awk '{print $1}'` ;

If you type that exactly as shown on the command line then your shell will
interpret \| as a file name. As shown, perl will interpolate $1 to whatever
$1 contains. You want:

$contents = `ls "$_" | wc -l`;

But that won't include "hidden" files in the count!

print $contents if ($contents != 0) ;
}

John

 

[Tad McClellan]

I am trying to use "pipe" as in the unix command line sense in Perl
below:


for(`ls $ARGV[0]`)

What happens if $ARGV[0] eq ';rm -rf /' ?

The same thing that would happen if the user had typed that
same argument on its own command line.

 

[xhoster]

Hi


I am trying to use "pipe" as in the unix command line sense in Perl
below:



for(`ls $ARGV[0]`)

What happens if $ARGV[0] eq ';rm -rf /' ?

The same thing as happens if you type 'rm -rf /' on the command line.

Xho

 

[xhoster]

Hi

I am trying to use "pipe" as in the unix command line sense in Perl
below:

for(`ls $ARGV[0]`)

{

$contents = `ls $_ \| wc \| awk '{print $1}'` ;

print $contents if ($contents != 0) ;

}

The immediately problem is that you are not stripping the new line from
the results of the first ``. But you are surely going about this the wrong
way in the first place, as others have pointed out.


Xho

 

[usenet]

I am trying to use "pipe" as in the unix command line sense

This approach makes no sense, command-line or otherwise.

$contents = `ls $_ \| wc \| awk '{print $1}'` ;

perldoc -q "How do I count the number of lines in a file"

 

[usenet]

$contents = `ls $_ \| wc \| awk '{print $1}'` ;

Oh, and FWIW, you should be able to do "wc -l" (show linecount only,
instead of wc | awk '{print $1}'). But don't do that in Perl.