Shell Programming and Scripting

See my post #2 in this thread, where exactly this is explained. Replace the "echo"-commands i put in to show the mechanism with some other commands, namely the mail-command if you want to send an email. (And, as always, see man mail for details about how to use the command.)

I hope this helps.

bakunin

awesome its looking really good now -

Code:

#!/bin/bash
cd /to_be_archived/
for DIR in * ; do
fSaveDir="${DIR##*/}"
tar -cf "${fSaveDir}".tar "${fSaveDir}"
rsync -a "${fSaveDir}".tar /archived_projects/
if [ $? -ne 0 ]
then
mail -s "${fSaveDir}" robertw@molinare.co.uk <<< "project "${fSaveDir}" aborted due to error"
else
rm -f "${fSaveDir}".tar
rm -rf "${fSaveDir}"
fi
done

few questions tho,

lets say i have tons of projects in the "to_be_archived" folder and the script runs and it fails on a job number 2 out of 20 does that mean the script will exit out completley or will it carry on with the other folders?

few answers:

first, the script will continue because it will exit only if you tell it so look at its code (properly indented, as i told you to do) and its structure becomes clear (i have shortened some lines to not overflow the screen:

Code:

#!/bin/bash
cd /to_be_archived/
for DIR in * ; do                V do this for every value of DIR:
     fSaveDir="${DIR##*/}"       |
     tar -cf [...]               |
     rsync -a [...]              |
     if [ $? -ne 0 ] ; then      |  V do this if the previous cmd failed:
          mail -s [...]          |  |
     else                        |    and this, if not:
          rm -f [...]            |  |
          rm -rf [...]           |  |
     fi                          |
done

You see what it does - it will do exactly that, nothing more, i promise! If you don't tell it to exit under cetain circumstances, it won't (should you want that: put an "exit" command in somewhere).

For a beginner you have done very good work. (sorry, if that sounds condescending, it isn't meant that way. Programming is like playing chess: you spend half an hour to learn the rules and then a lifetime to really play the game well.)

Now for some of the finer points: the variable "$?" is set anew after each command. This means that this part:

Code:

tar -cf "${fSaveDir}".tar "${fSaveDir}"
rsync -a "${fSaveDir}".tar /archived_projects/
if [ $? -ne 0 ] ; then
     [....]

might not exactly do what you want: suppose the tar-command encounters a problem. It would exit, set an error code which you do not observe, then the rsync-command will start and eventually do its job and you will never be notified about the problem the tar-command had. Even worse, the rsync-command would overwrite the last good copy you had in the archive with the faulty tar-file you just produced.

A big part of the art of script programming is to foresee what could possibly go wrong and take measures against that. You do not necessarily have to program a solution to a problem, but you want to become aware of it!

If a script has to do a, b, c and d you want to see as outcome that it did a and b, couldn't do c (ideally by giving the reason why) and therefore did not even try d. The last thing you want is the script to not recognize it didn't do c, attempt to do d (which would make no sense at all because it builds on the result of the previously run c), eventually "succeed" doing it (but with a completely unusable result) and telling you "all done successfully".

Look back at my model script from post #2: i looked at the return code of every command and put different error information for each command failing in. You do not have to exit the script as i did, but you should do something about a failing command and most probably stop the processing of the part at hand.

I hope this helps.

bakunin

Makes sense, so if i dont put an exit command it will continue regardless?

So really i want an exit line here

Code:

mail -s "${fSaveDir}" robertw@molinare.co.uk <<< "project "${fSaveDir}" aborted due to error"
EXIT
else

and also i want to do another if, then, else statement for the tarring?

lets say i have multiple project folders in the "to_be_archived" folder and this script runs on the 1st folder and produces an error code for the tar and emails me and exits

will it exit the script, or will it carry on and do the 2nd project folder?

If you're in a loop (such as for or while or until) and you want to exit the script containing the loop, use exit.

If you're in a loop and you want to stop processing the loop and continue with program steps after the loop, use break.

If you're in a loop and you want to stop processing the current iteration of the loop and continue with the next iteration, use continue. This is only needed if there are other steps in the current iteration of the loop you want to skip. The default behavior when hitting the done at the end of a loop is to continue with the next iteration of the loop if there are additional values to be processed by the loop.

Can i just use an if statement and not an if or else statement,

If / Else Statements (Shell Scripting) - Code Wiki

If you only care about what happens when the if condition is true and don't want to do anything if the condition is false, then you don't need the else clause in your if statement.