PHP exec Java on Windows produces no output

Question

I've read through a lot of similar SO questions about my issue, none seem to have my issue. If it's relevant, I'm running PHP 5.3.8 on Apache 2.2 and PHP exec() runs as nt authority\system

$cmd = "java -version";
$res = exec($cmd, $output, $return);

var_dump($res, $output, $return);

Produces:

string '' (length=0)

array
    empty

int 0

$return being 0 hints that this was successful. Interestingly, if I run:

$cmd = "java -version 2> response";

A file is created with the expected output:

java version "1.6.0_24"
Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)

So my question: Why is $output not getting populated?

Comment update

Result of $res = exec("dir c:", $output, $return);

string '               2 Dir(s)  335,636,791,296 bytes free' (length=51)

array
    0 => string ' Volume in drive C is Local Disk' (length=32)
    1 => string ' Volume Serial Number is D87C-E25C' (length=34)
    2 => string '' (length=0)
    ...
    12 => string '               5 File(s)          1,158 bytes' (length=45)
    13 => string '               2 Dir(s)  335,636,791,296 bytes free' (length=51)

int 0

please check my updated answer, hope it will fix it for you

Hawili
– Hawili

2012-09-04 11:17:12 +00:00
Commented Sep 4, 2012 at 11:17 — Hawili
– Hawili, Commented Sep 4, 2012 at 11:17

Hawili · Accepted Answer · 2012-09-04 11:01:25Z

8

try this

$output = `java -version 2>&1`

watch for the backticks around the command, it serves exactly as shell command

2>&1 should redirect error to stdout since java by default use stderror !

edited Sep 4, 2012 at 11:01

answered Sep 4, 2012 at 9:19

Hawili

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3 Comments

cloakedninjas Over a year ago

Tried that $output is just null

Hawili Over a year ago

can you try something like `dir c:`

cloakedninjas Over a year ago

edited main question with output - all good - no issues with execution

Marcin Orlowski · Accepted Answer · 2012-09-04 09:23:22Z

0

You seem to compare apples with oranges as in second example you redirect stderr stream while you do not do that in first case. I suggest to always redirect stderr to stdout while using calls like exec otherwise you will lose this output

answered Sep 4, 2012 at 9:23

Marcin Orlowski

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1 Comment

cloakedninjas Over a year ago

But why is output going to stderr? According to PHP the command executed successfully - note $return = 0

cloakedninjas · Accepted Answer · 2012-09-10 13:02:47Z

0

While not an "answer" - what I ended up doing was to redirect all output to STDOUT and check $return for 0.

This may be related to this bug, even though I'm running 5.3 it seems to match my scenario

answered Sep 10, 2012 at 13:02

cloakedninjas

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