How do I customize a script from "Wicked Cool Shell Scripts"?
Regarding script #41 (calculating available disk space), out of your book Wicked Cool Shell Scripts, I am unclear how I can have this script calculate the free space on one specific drive, namely /Volumes/Documents HD in my case.
I'd also love to know how I can automatically email the results of this same script, say every 24 hours. If you could kindly point me in the right direction, I'm sure I could figure out the rest!
This is a fairly straightforward script you've asked about, so this will be an easy explanation.
The most important line in the diskspace script is:
df -k | awk -f $tempfile
Let's just run a quick df -k so you can see the output in question:
$ df -k Filesystem 1K-blocks Used Avail Capacity Mounted on /dev/disk0s9 156277884 63170972 92850912 40% / devfs 101 101 0 100% /dev fdesc 1 1 0 100% /dev <volfs> 512 512 0 100% /.vol /dev/disk1s3 156159792 138235824 17923968 89% /Volumes/X2 automount -nsl  0 0 0 100% /Network automount -fstab  0 0 0 100% /automount/Servers automount -static  0 0 0 100% /automount/static
The important thing to see here is that I have one non-root drive, /Volumes/X2, and that it shows up in the list exactly in that format.
This means that you can weed out other drives by using a call to grep. I'd tally up all drives on /Volume by doing this:
df -k | grep /Volumes | awk -f $tempfile
You could be even more specific, by using your hard disk name too:
df -k | grep /Volumes/Documents\ HD | awk -f $tempfile
Either way, changing that one line should accomplish what you seek.
In terms of automatically emailing the results every 24 hours, that's a job for crontab. Start with man crontab and you'll find that it's not too terribly hard to figure out.
If you would like to learn more about crontab and related administrative features of Unix, I suggest my brand new fourth edition of Teach Yourself Unix in 24 Hours.
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