[Ilugc] difference between interactive and background cron script

[Girish Venkatachalam]

On 17:16:16 Oct 09, Mohan Sundaram wrote:
> I've written a bash script to get my SSID and accordingly set my network
> preferences (on a Mac). The script works well in an interactive shell but
> fails to work similarly when invoked thro cron.
> ssid = `networksetup -getairportnetwork| cut -d : -f 2`
> echo $ssid ESSID found.
> 
> gives me the SSID of my access point. Output is
> MOHAN-DSL ESSID found.
> 
> script contents:
> ssid = `networksetup -getairportnetwork| cut -d : -f 2`
> echo $ssid ESSID found.
> 
> is invoked using */3 * * * * script > logfile in crontab. cat logfile shows
> just
> ESSID found.
> 
> Any pointers?
> 

cron(8) cannot use STDIO, STDOUT or STDERR. All point to /dev/null.

So it is AFAIK impossible to run interactive programs using cron.

First check whether your script works in a batch fashion rather than
interactive. Then you can get it working with cron.

Of course you need to give full path for 'networksetup'.

-Girish