Running shell_exec('which java') in PHP return nothing

Question

If I run

which java

from the command line I get the proper input (/usr/java/.../bin/java). However if I run it in a php script:

<?
  echo 'java. ' . shell_exec('which java');
  echo 'ls. ' . shell_exec('which ls');
?>

nothing gets printed out for which java but I get the proper results for which ls...

The server process doesn't have it's path environment variable set. — Byron Whitlock
– Byron Whitlock, Commented Sep 24, 2010 at 19:33
If I send the hardcoded path it works. I then tried to include it in a bash file script with the environment setup and it didn't work either... — Stephane Grenier
– Stephane Grenier, Commented Sep 25, 2010 at 16:05

Stephane Grenier · Accepted Answer · 2011-07-03 02:30:10Z

2

Two things were needed:

the full path to the JVM (it wasn't set in the environment)
" 2>&1" at the end of the command line.

So for example:

echo shell_exec('/usr/java/jdk6/bin/java -cp myJars.jar MyMainClass arg1 2>&1");

answered Jul 3, 2011 at 2:30

Stephane Grenier

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giorgio79 Over a year ago

Thanks, just what I was looking for during the past 30 minutes. Adding the 2>&1 worked. Not sure why though...

jimp · Accepted Answer · 2013-04-18 15:23:40Z

1

I just ran into this problem as well. I was trying to determine if the qrencode utility is installed on the (any) server, and if not then log/warn/exit gracefully.

Considering the program should always be in a standard path, I prefixed the which command with the likely locations of the binary, while still respecting that $PATH might be somehow defined on the system. I think you could use this approach with common Java paths, too:

shell_exec('PATH="$PATH:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin" '.
           'which qrencode');

answered Apr 18, 2013 at 15:23

jimp

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