PHP: Why isn't exec() returning output?

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I'm writing a PHP script to be used to check for network connections with Linux shell command ping calling it with PHP's exec():

<?php


// Bad IP domain for testing.
$domain_bad = "lksjdflksjdf.com";

$ip_address = $domain_bad;

exec("ping -c 1 $domain_bad", $output, $return_var);

var_dump($return_var);
echo "return_var is: $return_var" . "n";
var_dump($output);


exit;
?>

I'm not getting the output for the error message from ping in $output which is what I'm expecting:

$ php try.php
ping: unknown host lksjdflksjdf.com
int(2)
return_var is: 2
array(0) {
}

If the domain is a good domain, such as yahoo.com, then $output has the output from ping in an array. But if it's an error such as 'ping: unknown host lksjdflksjdf.com' it doesn't get returned to the $output array.

Why is this happening and is there a better method to do this?

Answers

You should redirect stderr to stdout.

To do that, change your exec() call like this:

exec("ping -c 1 $domain_bad 2>&1", $output, $return_var);

More info about 2>&1 meaning here.

Wednesday, August 10, 2022

sharisandhu786-28182fa5a444

Problem solved with the following command:

$WshShell = new COM("WScript.Shell");
$oExec = $WshShell->Run("C:wampbinphpphpVERSIONNUMBERphp-win.exe -f C:/wamp/www/path/to/backgroundProcess.php", 0, false);

Friday, December 9, 2022

eusebiojrperezcolon-2ca1e31143e1

Does your computer have UAC turned off? (Windows 7 or Vista, accessing C: with out UAC perms will error so for ease turn it off),

Secondly, exec requires a string input,

Thirdly need to be escaped as Phill said

exec('java -jar "C:/batik/batik-rasterizer.jar" -m C:/pathto/image/png -d 
"C:/pathtoimg/temp/2fa8af078803491746235057c546c1b6.png" -w 800 
"C:/pathtoimg/temp/2fa8af078803491746235057c546c1b6.svg"');

UPDATED FOR COMMENT ON PHILLS

Check that your allowed to use exec/system/backticks, using the CLI

Create a php file with <?php exec("echo hello"); ?> inside it save it
Then start CMD,
open a new window (open up my/ computer) and browse to your php.exe application
copy the address of the folder where you found it
in cmd type "cd " without quotes and after that right click and click pase then hit enter
type "php " (again without quotes) drag php file saved to the cmd box and drop it
then hit enter and see if it says hello in the cmd box

if this does not work check java is working without path to exe, in the cmd windows type your java --help and see if it works

Tuesday, August 2, 2022

florian_margaine

this is just a guess; I've written years ago a very wobbly chat script that used output buffering as well (and fetching new messages in while(true) loop) ..

While doing this I've encountered the same problems that sometimes the script stalled (blank screen), sometimes it took a while until the characters appeared and additionally this was also browser specific.

Here are the relevant code snippets I've added to the script to have it work with IE6 and FF2 (as I said, years ago ...)

<?php
    // End output buffering
    ob_end_flush(); 

    // IE and Safari Workaround
    // They will only display the webpage if it's completely loaded or
    // at least 5000 bytes have been "printed".
    for($i=0;$i<5000;$i++)
    {
        echo ' ';
    }

    while( ... )
    {
        echo 'Message';
        ob_flush();
        flush();
    }
?>

It worked for me, so maybe you could give it a try as well. (Altough I have no idea how modern browsers and server infrastrucutre will behave to this).

Sunday, December 4, 2022

kperryua

shell_exec returns all of the output stream as a string. exec returns the last line of the output by default, but can provide all output as an array specifed as the second parameter.

See

http://php.net/manual/en/function.shell-exec.php
http://php.net/manual/en/function.exec.php

Friday, October 14, 2022

gunalmel

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PHP: Why isn't exec() returning output?

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