stream_select
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.
stream_set_blocking
(PHP 4 >= 4.3.0, PHP 5)
stream_set_blocking — Set blocking/non-blocking mode on a stream
Description
bool stream_set_blocking
( resource
$stream
, int $mode
)
Sets blocking or non-blocking mode on a stream.
This function works for any stream that supports non-blocking mode (currently, regular files and socket streams).
Parameters
-
stream -
The stream.
-
mode -
If
modeis 0, the given stream will be switched to non-blocking mode, and if 1, it will be switched to blocking mode. This affects calls like fgets() and fread() that read from the stream. In non-blocking mode an fgets() call will always return right away while in blocking mode it will wait for data to become available on the stream.
Return Values
Returns TRUE on success or FALSE on failure.
Changelog
| Version | Description |
|---|---|
| 4.3.0 | Prior to PHP 4.3.0, this function only worked on socket based streams. |
Notes
Note:
This function was previously called as set_socket_blocking() and later socket_set_blocking() but this usage is deprecated.
See Also
- stream_select() - Runs the equivalent of the select() system call on the given arrays of streams with a timeout specified by tv_sec and tv_usec
add a note
User Contributed Notes
stream_set_blocking - [4 notes]
MagicalTux at ookoo dot org ¶
6 years ago
Anonymous ¶
3 months ago
On Windows this function does not work with pipes opened with proc_open (https://bugs.php.net/bug.php?id=47918, https://bugs.php.net/bug.php?id=34972, https://bugs.php.net/bug.php?id=51800)
t dot starling at physics dot unimelb dot edu dot au ¶
7 years ago
Warning: if you write too much data to a stream in non-blocking mode and fill the buffer, the excess will be silently discarded. Observed in PHP 4.4.0 under linux.
nmmm at nmmm dot nu ¶
4 months ago
It took me long time to "compile" this code,
thanks to set blocking, we can write and read at the same time in proc_open().
Notice how the output from child begins after we feed several lines into it.
Also notice that end lines are output *after* we do
fclose($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--");
}
?>