stream_set_blocking

Anonymous (2013-01-04 07:38:01)

On Windows this function does not work with pipes opened with proc_open (https://bugs.php.net/bug.php?id=47918, https://bugs.php.net/bug.php?id=34972, https://bugs.php.net/bug.php?id=51800)

nmmm at nmmm dot nu (2012-12-02 20:11:55)

It took me long time to "compile" this code,
thanks to set blocking, we can write and read at the same time in proc_open(). 

Notice how the output from child begins after we feed several lines into it.

Also notice that end lines are output *after* we do

fclose($pipes[0]);

Then we need to continue read until feof(), because fgets() may return false even there are more data to read.

For educational reasons, I suggest you to try feeding small file (1-2 KB), medium file (4-5 MB) and huge file ( GB++ ).

#!/usr/bin/php
<?php
$max_buffer = 16 * 1024;

$prog = 'cat';

$descr = array(
    0 => array("pipe", "r"),        // stdin
    1 => array("pipe", "w"),        // stdout
    2 => array("file", "/dev/null", "a")    // stderr
);

$process = proc_open($prog, $descr, $pipes);

foreach($pipes as $f)
    stream_set_blocking($f, 0);

//stream_set_write_buffer($pipes[0], 1*1024*1024);

$br = 0;
while ( ($line = fgets(STDIN, $max_buffer)) !== false){
    $br = $br + strlen($line);
    
    $ret = fwrite($pipes[0], $line);
    
    if ($ret == false){
        echo "error, buffer full?\n";
    }
    
    $s = fgets($pipes[1], $max_buffer);

    printf("%12.3f | ", $br / 1024);
    process_output($s);
}

//stream_set_blocking($pipes[1], 1);
fclose($pipes[0]);
    

while (! feof($pipes[1]) ){
    $s = fgets($pipes[1], $max_buffer);
    if ($s === false)
        continue;

    printf("%12s |", "end");
    process_output($s);
}

fclose($pipes[1]);

function process_output($s){
    $s = trim($s);

    if (strlen($s) > 50)
        $s = substr($s, 0, 50) . " [crop]";

    printf("%s\n", $s ? $s : "--none--");
}
?>

MagicalTux at ookoo dot org (2006-09-07 23:13:49)

When you use fwrite() on a non-blocking stream, data isn't discarded silently as t dot starling said.
Remember that fwrite() returns an int, and this int represents the amount of data really written to the stream. So, if you see that fwrite() returns less than the amount of written data, it means you'll have to call fwrite() again in the future to write the remaining amount of data.
You can use stream_select() to wait for the stream to be available for writing, then continue writing data to the stream.
Non-blocking streams are useful as you can have more than one non-blocking stream, and wait for them to be available for writing.

t dot starling at physics dot unimelb dot edu dot au (2005-09-08 04:02:07)

Warning: if you write too much data to a stream in non-blocking mode and fill the buffer, the excess will be silently discarded. Observed in PHP 4.4.0 under linux.