Question

When I execute my command in PHP with shell_exec it always returns an empty string. I tried shell_exec('ls -l'); and it works. I put the command as a separate file and still same result.

$shellOutput = shell_exec("pacmd list-sinks | grep 'volume: 0:' | tail -1 | awk '{ print $3 }'");

//return execute status;
echo trim($shellOutput); 

Answer 1

I changed the sudoers to
ALL ALL = (ALL) :NOPASSWD ALL (very un-secure, but just to find something sure to work),

then I did a

sudo -u myusername /path/to/script.sh

where script.sh
has
export VAR=value
export VAR=value

for all the environmental variables that are necessary (you can do a printenv from a user who can properly pacmd to see what you need. probably a good HOME and maybe an XAUTHORITY).

hope that helps