Suppressing output from exec() calls in PHP

Question

I have a number of command line scripts in PHP that use exec() to perform tasks such as restarting services, loading MySQL timezone files, etc. While exec() itself does not

Answer 1

Just redirect stderr to /dev/null

$command = 'mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql mysql 2>/dev/null';

or to stdout

$command = 'mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql mysql 2>&1';

Answer 2

According to http://us3.php.net/manual/en/function.shell-exec.php you can assign this command's output to a variable.

You don't necessarily have to do anything with the variable, which means you are effectively suppressing output.

Hope that helps!

Answer 3

Redirecting stderr alone should not influence where processing takes place, just make sure not to add an &. It should only run in the background if you redirect the output and make it run in the background.

Edit:

Cracked open cygwin, you need to redirect stderr for the first command, give this a try:

$command = 'mysql_tzinfo_to_sql /usr/share/zoneinfo 2> /dev/null | mysql mysql';
exec($command, $output, $result);

Answer 4

Redirecting to /dev/null does not cause PHP to stop waiting for the command. Adding a & does do this, you probably associate the two because the final & is often used in conjunction with a redirect.

In response to Yannick's (deleted) comment: it seems if you want to run something in the background in PHP, you must redirect as well as using &. This does not mean that redirection alone causes it to run in the background.