It works for me . Thanks
Sudhakar Gajjala
Chris Devers <[EMAIL PROTECTED]> on 08/30/2004 10:47:55 PM
Please respond to [EMAIL PROTECTED]
To: Sudhakar Gajjala/C/[EMAIL PROTECTED]
cc: [EMAIL PROTECTED]
Subject: Re: How do i run shell command
On Mon, 30 Aug 2004 [EMAIL PROTECTED] wrote:
> I was trying to run System command from my perl Script . As i have pipe
( |
> Anybody help me how to run shell command in Perl
>
> Here is the command : system "cat $filename | wc -l";
You realize, of course, that this can be done entirely in Perl ?
Quoting from the excellent _Perl Cookbook_:
[...] you can emulate wc by opening up and reading the file yourself:
open(FILE, "< $file") or die "can't open $file: $!";
$count++ while <FILE>;
# $count now holds the number of lines read
Another way of writing this is:
open(FILE, "< $file") or die "can't open $file: $!";
for ($count=0; <FILE>; $count++) { }
If you're not reading from any other files, you don't need the $count
variable in this case. The special variable $. holds the number of
lines read since a filehandle was last explicitly closed:
1 while <FILE>;
$count = $.;
This reads all the records in the file and discards them.
But if you really do need to do this via a system command -- you don't,
but I'll play along -- then the command as you've given it is what is
known as a Useless Use Of Cat.
This command --
cat file | wc -l
-- is equivalent to this one --
wc -l file
-- but the latter invokes less overhead, and so should be a bit faster.
Unless you really are conCATenating a chain of files together, most
commands of the form "cat foo | cmd" can be rewritten as "cmd foo" or,
maybe, "cmd < foo".
--
Chris Devers [EMAIL PROTECTED]
http://devers.homeip.net:8080/blog/
np: 'It's Not Easy Being Green (lo-fi midi version)'
by Kermit
from 'The Muppet Movie Soundtrack'
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