spiralofhope

So I've been farting around after a long break from doing much of anything on Linux.  I was prompted by my new hard drive arriving.

I spent some time migrating data from five separate hard drives and a stack of DVDs.  One of my next goals was to get backups working, so that I can back up from my SSD to this new drive.

I have an old backup script, but I decided that I could spend this afternoon screwing around with it to optimize it a little.

Using the wonderful mcedit which comes with Midnight Commander, I hacked away.  Linux being what it is, there was a tangled horror of stuff I needed to try to remember, look up through my notes, get answers to and/or figure out.

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I've done enough scripting in the past that I've got notes on most of the common stuff.  But because I wanted to "optimize" my backup code by replacing duplication with re-usable procedures, and I wanted to make it generally smarter, I really did need to do some research to get a bunch of other stuff working.

Keep in mind that all of this is quick-and-dirty.  Oh, and WordPress doesn't preserve space-tabbing or give coloured markup.  Meh.

Procedure/function ∞

example() {
echo hi!
}
example

Pass parameters to a procedure/function ∞

example() {
  echo some text $1
}
example "my text"

Pass an array to a function, iterate through an array ∞

example() {
  for element in ${@[@]}; do
    echo some text $element
  done
}
example  "my text" two 3

A case ∞

var=2
case $var in
  1)
    echo "one"
  2)
    echo "two"
  ;;
  *)
    echo "everything else"
  ;;
esac

if/not ∞

var=2
if [ $var -ne 2]; then
  echo "nope!"
fi

Error Trapping (^c/BREAK) ∞

How do I trap error codes? (INT, aka ^c/BREAK)

This can get much much more complex, but a simple example is:

trap breaktrap INT
breaktrap() {
  echo "do this when ^c is used"
}

I also leveraged the procedure and used it like one.. letting me do some pretty nifty stuff because I already had some other error-detection code.  Yes, I harden my code.

Learning a partition's filesystem ∞

Ever notice how [s|c|]fdisk has partition types?  Well here's how you can get at them!

\sfdisk  --part-type /dev/sda  1

• 7 = NTFS
• 82 = Swap

• 83 = Linux (ext2/ext3/etc)

Is a partition mounted? ∞

2019-10-05 - I'm not really sure what I was trying to accomplish here..

How do I learn if a partition is mounted? /proc/mounts? nope! That mysteriously doesn't show your present root filesystem.

Since fsck is retarded, I had to pipe other programs and wrap all that shit around fsck to build the fucking feature for it.

for line in `df | cut -d' ' -f1`; do
  if [ "x$1" -ne "x$line" ]; then # not mounted
    /sbin/fsck /dev/sda1
  fi
done

How do I get fsck to just skip on already-mounted partitions? (Can't do it) ∞

[edit 2012-09-03] I could probably script a workaround, but there's nothing provided.

2019-10-05 - Just leverage is-partition-mounted.sh

Last updated 2019-10-05 at 09:53:41