Question

I’m have some php code:

<?
$cmd="mkfifo /tmp/myfifo;";
system($cmd);
$cmd="echo 1 > /tmp/myfifo 2>&1 &";
system($cmd);
?>

on an apache server. I want to have the second command not block. According to the info page of system:

If a program is started with this function, in order for it to continue running 
in the background, the output of the program must be redirected to a file or 
another output stream. Failing to do so will cause PHP to hang until the execution 
of the program ends.

But I don’t see how to apply that to this situation. I tried

$cmd="echo 1 > /tmp/myfifo > /dev/null 2>&1 &";

But to be honest that seems nonsensical.

EDIT:

My ultimate goal is to write to a fifo that may never be read from, and time out the write after 5 seconds. So, if I can manage to get this command to not block the php executition, I can sleep 5 seconds and then cat /tmp/myfifo > /dev/null 2>&1 to unblock the original write.

Can anyone think of a better way to have my write not hang indefinitely (in neither the background nor the foreground)?

Answer 1

If you need to write to a file (and prevent other processes from writing until you are done), then just use file_put_contents.

<?php
// The new person to add to the file
$person = "John Smith\n";

// Write the contents to the file, 
// using the FILE_APPEND flag to append the content to the end of the file
// and the LOCK_EX flag to prevent anyone else writing to the file at the same time
file_put_contents('/tmp/myfifo', $person, FILE_APPEND | LOCK_EX);