The “E” editor for Windows adds support for in/out pipes in today’s release:

cat records.txt | sort | e | process_records

I’m working on extending Textpattern with some scripts I developed for Blosxom. Textpattern is a Php-based weblogging tool, and my scripts are all Perl-based plugins and command-line utilities. I don’t really want to port the scripts to Php, so I decided to find a way to call Perl from Php.

In a few minutes of searching, I only found one Perl binding for Php. It isn’t considered stable, and it isn’t available from my web host (Dreamhost). I did find an answer in the Php manual, but a googling on the specific topic of calling Perl from Php came up dry. So I decided to make it a bit more obvious.

Pipe dreams

All of my scrips are simple text processors, so the inputs and outputs can be passed using the stdin/stdout pipes. Using both the input and output pipes of a process is a bit more than the standard Php exec functions can handle, so we’ll be using the proc function family. Nearly every language has a set of these functions (and that’s a good thing).

You can download the demo script here. The script will need to be executable, it needs the correct path to the Perl interpreter, and the log file folder needs to be writable by the web-server process.

The Perl script reads text from stdin, and replaces spaces with underscores. From Php, we can call the Perl script and manage the standard in, out, and error pipes. The example is slightly modified from the Php manual.

The basic process:

1. Define what to do with the process’s pipes. Notice that the error pipe is mapped to a log file (which is appended on each call).
2. Define some text to test with the Perl script.
3. Open the process, which is our Perl script. This will fail if the script can’t be found, or if it isn’t executable.
4. Write the test text to the input pipe of the Perl script.
5. Read the output of the Perl script.
6. Close the process. This is best done after all of the pipes are closed (otherwise it causes deadlock).

The PHP script:

< ?php
$handles = array(                             // 1
   0 => array("pipe", "r"),                   // stdin 
   1 => array("pipe", "w"),                   // stdout 
   2 => array("file", "test-errors.txt", "a") // stderr 
);  
$test_text = "This is a test";
    
$process = proc_open("./test.pl", $handles, $pipes);
if (is_resource($process)) {
    fwrite($pipes[0], "$test_text");
    fclose($pipes[0]);    
    while (!feof($pipes[1])) {
        $output .= fgets($pipes[1], 1024);
    }
    fclose($pipes[1]);    
    $r = proc_close($process);    
    echo "Before: $test_text<br />";
    echo "After : $outputn<br />";
}
?>

And the perl script:

#!/usr/local/bin/perl

# replace spaces with _s in stdin
while(<>) {
    s/ /_/g;
    print;
}