php shell_exec wait for output

php exec command (or similar) to not wait for result

stackoverflow.com › questions › 3819398 › php-exec-command-or-similar-to-not-wait-for-result

From the documentation:

In order to execute a command and have it not hang your PHP script while
it runs, the program you run must not output back to PHP. To do this,
redirect both stdout and stderr to /dev/null, then background it.

> /dev/null 2>&1 &

In order to execute a command and have
it spawned off as another process that
is not dependent on the Apache thread
to keep running (will not die if
somebody cancels the page) run this:

exec('bash -c "exec nohup setsid your_command > /dev/null 2>&1 &"');

Answer from Cristian on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 3819398 › php-exec-command-or-similar-to-not-wait-for-result

php exec command (or similar) to not wait for result - Stack Overflow

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1 of 7

148

From the documentation:

In order to execute a command and have it not hang your PHP script while
it runs, the program you run must not output back to PHP. To do this,
redirect both stdout and stderr to /dev/null, then background it.

> /dev/null 2>&1 &

In order to execute a command and have
it spawned off as another process that
is not dependent on the Apache thread
to keep running (will not die if
somebody cancels the page) run this:

exec('bash -c "exec nohup setsid your_command > /dev/null 2>&1 &"');

2 of 7

You can run the command in the background by adding a & at the end of it as:

exec('run_baby_run &');

But doing this alone will hang your script because:

If a program is started with exec 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.

So you can redirect the stdout of the command to a file, if you want to see it later or to /dev/null if you want to discard it as:

exec('run_baby_run > /dev/null &');

PHP

php.net › manual › en › function.shell-exec.php

PHP: shell_exec - Manual

If you're trying to run a command such as "gunzip -t" in shell_exec and getting an empty result, you might need to add 2>&1 to the end of the command, eg: Won't always work: echo shell_exec("gunzip -c -t $path_to_backup_file"); Should work: echo shell_exec("gunzip -c -t $path_to_backup_file 2>&1"); In the above example, a line break at the beginning of the gunzip output seemed to prevent shell_exec printing anything else. Hope this saves someone else an hour or two. ... To run a command in background, the output must be redirected to /dev/null. This is written in exec() manual page. There are cases where you need the output to be logged somewhere else though. Redirecting the output to a file like this didn't work for me: <?php # this doesn't work!

Discussions

How to Wait for completion of shell commands execution in PHP? - Stack Overflow

i am executing long running shell commands using PHP. in a single php file i am calling a series of shell_exec function to execute long runnable commands. What's the problem is ,that i am getting a More on stackoverflow.com

stackoverflow.com

Executing Python Script from PHP and wait for it.

https://stackoverflow.com/questions/19735250/running-a-python-script-from-php Only found that but I guess you started by it More on reddit.com

r/PHPhelp

August 22, 2019

queue - PHP shell_exec wait for script to finish? - Stack Overflow

I have a PHP script that queries a database for a list of jobs to be done and fires off other PHP scripts based on what it finds in the database (basically a process queue). Some of the scripts t... More on stackoverflow.com

stackoverflow.com

September 3, 2011

shell script - Bash to Call PHP, Wait for PHP Process to finish? - Unix & Linux Stack Exchange

The way you have written it, it should wait until the script exits. Presumably, your php script is configured to be run in the background. Can you show us the contents of the PHP script? By the way, to check if it is running, use pgrep -f Cron-Run.php instead. ... Its a collecton of 34 Files all in all. the file i am attempting to execute ... More on unix.stackexchange.com

unix.stackexchange.com

March 2, 2016

Stack Overflow

stackoverflow.com › questions › 11524063 › php-shell-exec-wait-for-script-to-done

ffmpeg - PHP shell_exec wait for script to done? - Stack Overflow

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1 of 2

shell_exec is not the cause of your problems. It'll wait and return the output of your command. However, you mustn't start your command in the background and using nohup.

nohup is the command you are calling but as soon as it has started its child process it will exit immediatelly, thus, shell_exec will not wait for that process to be completed. You should also refrain from running the command in the background with &.

2 of 2

I'd first suggest not executing code from PHP but use PHP wrappers and libraries whenever possible.

One problem I see is that your processing is synchronous, this means the user will have to wait that the server responds without any clue about what is going on. He may even refresh the page which would increase the load of your server without control, and this is a very serious issue. This would enable a DOS attack.

I suggest AJAX for these long-running task. You can display something to show progress on the webpage and update it (AJAX) when it's done or switch to another page. You can even handle the case of the user quitting the page by catching that event in javascript and killing the process.

Linux Tip

linuxscrew.com › home › programming › php › php shell_exec function: how to use it [with examples]

PHP shell_exec Function: How to Use It [With Examples]

February 23, 2021 - $fileList = shell_exec('ls -la 2>&1'); echo "<pre>$fileList</pre>"; 2>&1 tells the shell to redirect stderr output to the current stdout – which resolves the issue. To run a command in the background, redirect the output to /dev/null – this sends the output to nowhere (effectively sending it to the abyss), rather than PHP waiting for the response, it will execute the code and resume running PHP immediately – the result from shell_exec will not be waited on, and will not be available to PHP.

Stack Overflow

stackoverflow.com › questions › 36576674 › how-to-wait-for-completion-of-shell-commands-execution-in-php

How to Wait for completion of shell commands execution in PHP? - Stack Overflow

PHP shell_exec update output as script is running · Share · Improve this answer · Follow · edited May 23, 2017 at 12:07 · CommunityBot · 111 silver badge · answered Apr 12, 2016 at 14:48 · Hyra · 82811 gold badge66 silver badges2222 bronze badges · Sign up to request clarification or add additional context in comments. Add a comment · 0 · shell_exec waits for command, so, problem is, as u think, you're calling it into background, maybe a nohup?.

reddit.com › r/phphelp › executing python script from php and wait for it.

r/PHPhelp on Reddit: Executing Python Script from PHP and wait for it.

August 22, 2019 -

I was working on something that requires me to run a Python script with some arguments from PHP itself, and complete some task and print some output. The thing is, I tried shell_exec() and few more things mentioned in SO to run python script. But, the issue is that PHP doesn't seem to wait for my python script to complete. I need something that'll wait till the Python is done with the job. Can someone suggest me something?

EDIT : Typo in "shell_exec()" name.

UPDATE : After I re-looked at my script this morning.... seems like python can't open file. So, the PHP might not have permissions for that script. So, went ahead and gave it the perms. I added "www-data" group to that python file and changed python file's perms to 777. It still didn't work. But, the main issue right now is that Python script can't seem to be executed via apache2->Php.

Thanks everyone for all the help and hints. Appreciate it!

UPDATE 2 : I fixed the permission issue with "www-data" and it's working. THANKS EVERYONE!

Top answer

1 of 3

https://stackoverflow.com/questions/19735250/running-a-python-script-from-php Only found that but I guess you started by it

2 of 3

I assume you mean shell_exec() cuz no clue what exec_shell() is. Strangely, i have always know shell_exec() waits and returns back the output because just a week ago i was looking for an async method (i didnt want it to wait)...the solution for async is radically different. This tells me python must be executing in a new process and returns back before its completed. You might want to check into ob_start( 'callback_func' ) and ob_end_flush() to capture all stdout of the python output. It won't wait but it could hint to you when its done based on the output you receive and then take action once you get back enough of the data you want (e.g. it ends in a certain way).

Stack Overflow

stackoverflow.com › questions › 7296288 › php-shell-exec-wait-for-script-to-finish

queue - PHP shell_exec wait for script to finish? - Stack Overflow

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1 of 1

Try this:

shell_exec("nohup /usr/bin/htmldoc -t pdf --webpage test.html > test.pdf 2>&1 &");

Our Code World

ourcodeworld.com › articles › read › 207 › how-to-execute-a-shell-command-using-php-without-await-for-the-result-asynchronous-in-linux-and-windows-environments

How to execute a shell command using PHP without await for the result (asynchronous) in Linux and windows environments | Our Code World

July 17, 2016 - If you use the command to execute ... as the default time limit is of 30 seconds. The system and shell_exec methods always expects for the output, there's no way to prevent it, however we use the trick to redirect a null output ...

Find elsewhere

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Stack Exchange

unix.stackexchange.com › questions › 267105 › bash-to-call-php-wait-for-php-process-to-finish

shell script - Bash to Call PHP, Wait for PHP Process to finish? - Unix & Linux Stack Exchange

March 2, 2016 - I was able to pause / wait for the process to finish by using the wait function. ... #!/bin/bash timestamp() { date +"%T" } pushd 'httpdocs/DIR1/DIR2'; file="Lock3.key" if [ -f "$file" ] then echo "$file found, Session is already in progress" $(date) else echo "$file was not found, Its safe to start the script" $(date) echo "Running Ebay Stock Only Script" $(date) #Its possible to double check if the script is running by checking memory. #ps aux | grep "php Cron-Run.php" (Not safe) php Cron-Run.php > Output.log wait echo "Finished Running Script, Lock file is deleted by PHP, Now exiting" $(date) fi exit

Stack Overflow

stackoverflow.com › questions › 7621348 › how-to-execute-shell-commands-synchronously-in-php

How to execute shell commands synchronously in PHP - Stack Overflow

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1 of 5

PHP exec will wait until the execution of the called program is finished, before processing the next line, unless you use & at the end of the string to run the program in background.

2 of 5

If I'm getting you right, you're executing php scripts from inside a php script.

Normally, php waits for the execution of the exec ("php phpscript1.php"); to finish before processing the next line.

To avoid this, just redirect the output to /dev/null or a file and run it in background.

For example: exec ("php phpscript1.php >/dev/null 2>&1 &");.

Stack Overflow

stackoverflow.com › questions › 1019867 › is-there-a-way-to-use-shell-exec-without-waiting-for-the-command-to-complete

php - Is there a way to use shell_exec without waiting for the command to complete? - Stack Overflow

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1 of 9

162

How about adding.

"> /dev/null 2>/dev/null &"

shell_exec('php measurePerformance.php 47 844 [email protected] > /dev/null 2>/dev/null &');

Note this also gets rid of the stdio and stderr.

2 of 9

This will execute a command and disconnect from the running process. Of course, it can be any command you want. But for a test, you can create a php file with a sleep(20) command it.

exec("nohup /usr/bin/php -f sleep.php > /dev/null 2>&1 &");

SitePoint

sitepoint.com › php

Long running PHP process waiting on shell exec - PHP - SitePoint Forums | Web Development & Design Community

July 29, 2010 - I have a PHP script that loops through a folder of images, for each image it adds some info to the database and resizes the image by making a shell call to ImageMagick. The problem is that this script takes a long time to execute since it waits for ImageMagick to resize each image before going ...

Stack Overflow

stackoverflow.com › questions › 6140107 › shell-exec-without-waiting-for-the-output › 6140302

php - shell_exec without waiting for the output - Stack Overflow

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1 of 1

This has been answered before at Asynchronous shell exec in PHP

Briefly:

shell_exec( $your_command . "> /dev/null 2>/dev/null &" );

Subinsb

subinsb.com › how-to-execute-command-without-waiting-for-it-to-finish-in-php

Execute Command Without Waiting For It To Finish - Subin's Blog

function <span style="color: red;">bgExec</span>($cmd) { if(substr(php_uname(), 0, 7) == "Windows"){ pclose(popen("start /B ". $cmd, "r")); }else { exec($cmd .

Stack Overflow

stackoverflow.com › questions › 39641793 › php-wait-for-exec-to-finish-and-output-the-result

api - PHP wait for exec to finish and output the result - Stack Overflow

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1 of 1

Have the PHP trigger an exec to a script that is forked so it runs in the background (ends with &). The page should then return some js that periodically polls the server via ajax requests to check the original script's status. The script should output its STDOUT and STDERR to unique file(s) so that the polling script can check the status.

Edit: If you need to know the script's exit code wrap it in another script:

#/bin/bash
uniqId=$1
yourscript $uniqId &
myPid=$!
echo $myPid > $uniqId'.pid'
wait $myPid
echo $? > $uniqId'.returned'

Call like ./wrapper.sh someIdUniqueToClient &. Untested, but you get the gist.

Dubbelboer

blog.dubbelboer.com › 2012 › 08 › 24 › execute-with-timeout.html

PHP shell_exec with a timeout - Erik's Code

<? /** * Execute a command and return it's output. Either wait until the command exits or the timeout has expired. * * @param string $cmd Command to execute. * @param number $timeout Timeout in seconds. * @return string Output of the command. * @throws \Exception */ function exec_timeout($cmd, $timeout) { // File descriptors passed to the process.

Piotr Horzycki

peterdev.pl › execute-a-shell-command-in-php

Executing shell commands from a PHP script | Piotr Horzycki - Java and PHP developer’s blog

April 2, 2021 - Such mechanism is commonly used in terminals, for example to paginate long output: ... In the example above, the output of the ls command was sent to the less command. If the ls failed, the chain would break and the second command would not be called. By default, we have to wait until each process terminates. This means our PHP script will also be paused when executing an external command.

reddit.com › r/phphelp › php shell_exec not working with pipes

r/PHPhelp on Reddit: php shell_exec not working with pipes

May 28, 2022 -

Hi all I'm trying to SvtAv1EncApp tools via web interface, I try to us both exec() shell_exec() with no success , BTW I print the command and run it into the shell directly and it's works perfectly fine.

$cmd2="/usr/local/bin/ffmpeg -loglevel -8 -i "$mp4" -s 960x540 -strict -1 -f yuv4mpegpipe - | /usr/local/bin/SvtAv1EncApp --no-progress -i stdin --rc 0 -q 38 --preset 8 -b stdout 2>/var/www/vl/ffmpeg.log | /usr/local/bin/ffmpeg -loglevel -8 -y -i - -i "$mp4" -map 0:v -map 1:a:0 -c:v copy $a '".$mpa."_.mkv' & ";

shell_exec( $cmd2 ) ;

Here is the text of echo $cmd2 output

/usr/local/bin/ffmpeg -loglevel -8 -i "FHD.mp4" -s 960x540 -strict -1 -f yuv4mpegpipe - | /usr/local/bin/SvtAv1EncApp --no-progress -i stdin --rc 0 -q 38 --preset 8 -b stdout 2>/var/www/vl/ffmpeg.log | /usr/local/bin/ffmpeg -loglevel -8 -y -i - -i "FHD.mp4" -map 0:v -map 1:a:0 -c:v copy -strict -2 -c:a libopus -b:a 64k 'FHD_.mkv' &

=Update=

I kinda solve it , I don't know why but exec() successfully executed the script , I created new bash script from command line thanks to @xisonc suggesting nano /usr/local/sbin/av1c with this value

!/bin/sh

touch /var/www/vl/ffmpeg.log /usr/local/bin/ffmpeg -loglevel -8 -i "$1" -s 960x540 -strict -1 -f yuv4mpegpipe -
| /usr/local/bin/SvtAv1EncApp --no-progress -i stdin --rc 0 -q 38 --preset 8 -b stdout 2>/var/www/vl/ffmpeg.log
| /usr/local/bin/ffmpeg -loglevel -8 -y -i - -i "$1" -map 0:v -map 1:a:0 -c:v copy -strict -2 -c:a libopus -b:a 64k "$2"

On the php script i had this

$cmd2="/usr/local/sbin/av1c '$mp4' '$mpa"."_.mkv'   2>/dev/null >/dev/null & " ; 
exec( $cmd2 , $pid, $r )    ;   
var_dump(  $r )                ;

var_dump returns 0 , and since the bash script are silent I don't need to see the output , ~~now I want to change it to wok on the background~~ it's running on background now after adding 2>/dev/null >/dev/null & at the end of the command .

Top answer

1 of 5

Did you really mean to put the ampersand there at the end? You do know what it does right?

2 of 5

Use the exec() function instead and make sure to provide the $output and $result_code arguments. Then, you'll be able to check the error to figure out the problem. Remember that from the web context, the user running the command is "www-data" (if installed as Apache mod-php) or whatever user you have configured for PHP-fpm. So, this could be a simple permission issue.

Medium

lakin-mohapatra.medium.com › achieve-parallel-processing-in-php-using-shell-exec-af99857d023c

Achieve parallel processing in php using shell_exec() | by Lakin Mohapatra | Medium

December 25, 2021 - The Client App asks the MQ Engine for a data (message) to be processed them in order (FIFO or based on priority) “you can also request data from specific queue". ... Now we will specifically discuss achieving parallel processing using shell_exec() command. // Set data which needs to be passed to separate process running php file. $arguments = [ 'data' => [], 'msg' => 'Test Message'];// Set Redirect output path to run php file in background rather than waiting for its output.