I'm using the exec function in PHP to run a command. The command I'm running can often take quite a bit of time and I don't have any need to read it's output. Is there a simple way of telling PHP not to wait for the exec command to finish before moving on with the rest of the script?
3 Answers
// nohup_test.php:
// a very long running process
$command = 'tail -f /dev/null';
exec("nohup $command >/dev/null 2>/dev/null &"); // here we go
printf('run command: %s'.PHP_EOL, $command);
echo 'Continuing to execute the rest of this script instructions'.PHP_EOL;
for ($x=1000000;$x-->0;) {
for ($y=1000000;$y-->0;) {
//this is so long, so I can do ps auwx | grep php while it's running and see whether $command run in separate process
}
}
run nohup_test.php:
$ php nohup_test.php
run command: tail -f /dev/null
Continuing to execute the rest of this script instructions
Let's find out pids of our processes:
$ ps auwx | grep tail
nemoden 3397 0.0 0.0 3252 636 pts/8 S+ 18:41 0:00 tail -f /dev/null
$ ps auwx | grep php
nemoden 3394 82.0 0.2 31208 6804 pts/8 R+ 18:41 0:04 php nohup_test.php
as you can see, pid is different and my script is running without waiting for tail -f /dev/null.
2 Comments
David Jones
Using
/dev/null was key to getting this working correctly. For some reason when I specified an actual log file location (i.e. /path/to/logfile as suggested by @zaf), PHP still waited for the process to finish. Any ideas why this is?
Nemoden
if you specify a log file like so:
exec("nohup $command >/tmp/my.log 2>/dev/null &"); and you run php nohup_test.php it doesn't print Continuing to execute the rest of this script instructions ? Because it works just fine or... should work so... It's really odd otherwiseHere is what I use (you can use exec or system instead of paasthru):
passthru("/path/to/program args >> /path/to/logfile 2>&1 &");
2 Comments
David Jones
Thanks! I'm not too familiar with some of the syntax here, though. What does the
>> and 2>&1 & do?
zaf
>> will send the output of the program to the log file. The '2>&1' will redirect error messages to the standard output, basically meaning all output will go to the log file. The '&' means run the command in the background.
What you are looking for is called an Asynchronous call, like answered here:
Asynchronous shell exec in PHP
php execute a background process
PHP exec() as Background Process (Windows Wampserver Environment)
1 Comment
David Jones
Thanks! I searched quite a bit for this before posting but apparently never used the right keywords...
&to the end of the command?exec("nohup $your_command &")- run command immune to hangups, output to non-tty (nohup), run it in background (&)