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working with other programs in perl

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# 1  
Old 01-08-2009
working with other programs in perl
Hi,

I'm still new to perl, and I'm trying to figure out how to work with data output from another program. For example, from a command line I can run "foo -xyz" and it will produce the output I am looking for, which is several lines of text that I will then parse and manipulate within the perl script.

I could redirect the output to a file and then read that file to do what I need to do, but isn't there a way to use the data directly.. line by line.. as it comes out? as STDIN perhaps?

-Decoy
# 2  
Old 01-08-2009
Code:
foo -xyz | perl '...'

# 3  
Old 01-08-2009
yes, but I'm trying to do it internal of the script.

I'm thinking:
Code:
$run=`foo -xyz`
@lines=split(/\n/,$run)

but I'm concerned with running into resource issues as sometimes the output of foo can be very large. I was hoping there was another approach.
# 4  
Old 01-08-2009
On your command line pipe the stdout of the command to the stdin in of your perl script:

Code:
foo | yourscript

then in yourscript do this:


Code:
# This loop reads from STDIN
    while (<>) {
       #do what you need to do with $_;
}

Example:

Code:
$ cat yourscript.pl
#!/usr/bin/perl

use strict;
use warnings;

while (<>) {
        print $_;
}

exit 0;

$ cal | yourscript.pl
    January 2009
Su Mo Tu We Th Fr Sa
             1  2  3
 4  5  6  7  8  9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31

Try these websites:

perlintro - perldoc.perl.org

Learn Perl - Learn Perl

perlfaq
# 5  
Old 01-08-2009
Do read line by line when running from inside a script use open
Code:
open $FOO, 'foo -xyz|';
while(<FOO>) {
    print $_;
}
close $FOO;

From perldoc -f open:
Quote:
If the filename begins with '|' , the filename is interpreted as a command to which output is to be piped, and if the filename ends with a '|' , the filename is interpreted as a command which pipes output to us.
# 6  
Old 01-08-2009
Thanks guys
# 7  
Old 01-09-2009
Code:
#! /usr/bin/perl
open FH,"cat a.txt|";
while(<FH>){
print $_;
}

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