Common Cron Problems

jenni

I am having problems getting a cron job to run and was wondering if anyone could direct me to a list of common problems with crons.

The script runs fine through the command line
The script has 755 permissions (the same as the other files that run through cron)
All of the other cron jobs run just fine
The script has the same owner as the other files

I am at a loss. Any ideas for other things I should check?

hessodreamy

I'm not that hot on cron jobs, but off the top of my head:

how are you running the job? are you calling a php file or a bash script? if php do you have the correct path to the php.exe?

is the script running at all? Do you have a mailto address set? This is just a line written in crontab like :
mailto=bob@hotmail.com

this should send you an email when the job runs. Then at least you know that it runs and you haven't got the scheduled time wrong.

Just a few suggestions. If you post some code I could look further.

samudasu

Are you running a command in your cron job that can only be run by root? That would explain why you can run it from the command line (if your logged in as root) and not from php/apache. I'm not sure that's the case but it's something to consider.

jenni

I have narrowed it down to a problem of connecting to the database. When I run it from the command line, I am logged in as just a user. It works perfectly. Cron runs as root.

Our database is on a different server. Is it possible that my user would be allowed to connect but not root?

samudasu

jenni wrote:
I have narrowed it down to a problem of connecting to the database. When I run it from the command line, I am logged in as just a user. It works perfectly. Cron runs as root.

Our database is on a different server. Is it possible that my user would be allowed to connect but not root?

Yes, this is totally possible. Some database installs don't allow root to connect from a remote location by default. Check your database manual.

jenni

I have confirmed with the DB admin that this is not the problem. I did find something else that was interesting though.

The error logs are reporting: PHP Fatal error: Call to undefined function: mysql_connect()

The error only occurs when the script is run through cron. Command line and browser are fine.

I found another thread on this forum where someone was having the opposite problem. Cron and Apache were referencing different versions of PHP.

I added #!/usr/local/bin/php at the top of my script, but it still does not work.

Any other suggestions?

samudasu

Post your script and your crontab line.

devinemke

jenni wrote:
The error logs are reporting: PHP Fatal error: Call to undefined function: mysql_connect()

that error suggests that the mySQL extension is not configured in the php.ini file. the fact that the script runs fine from the browser suggests that the cron daemon is running on a different physical machine than the web server (not uncommon on some commerical hosts).

jenni

We have our own dedicated servers, so I don't believe that cron is run on another server. However...I just had a big breakthrough...

I added this to the script and captured the output

shell_exec('which php');

When I ran the script through the command line, it returned: /usr/local/bin/php
When I ran the script through cron, it returned: /usr/bin/php

I tried adding #!/usr/local/bin/php to the top of my script so that it would grab the right php, but it did not work.

Is there another way to make it use the right version?

devinemke

not sure if this will make any difference but rather then putting the bang statement at the top of the script what i always do is use the path to the PHP binary with the script as a command line switch, like so:

0 0 * * * /path/to/php /path/to/script.php >/path/to/output.txt 2>/path/to/error.txt

jenni

Wahoo! Problem solved.

After a million combinations of possible solutions, something worked.

Add the path to PHP to the top of the script:
#!/usr/local/bin/php -q

Remove php from the cron tab
was:
10 11 php /fullpath/myfile.php
now:
10 11 /fullpath/myfile.php

Neither thing worked on its own, but combined together, everything appears to be aok.

Thank you for all of your responses. I really appreciate it.