Heredoc Rules When Using SQL Plus

I've been writing a lot of shell scripts lately, and usually they have included a here doc that invokes Oracle's SQL*Plus program.  Here docs can be very nice, but they can also be fairly flaky. You have to remember a bunch of strange rules when you write them or they will simply break with cryptic error messages.

I therefore created a list of here doc rules that I paste into every shell script that uses one.  Of course, this is a foolish way of recording knowledge, so I thought it might be useful to save them in my blog instead. Unfortunately, I've had to learn almost all of these rules myself the hard way, which sometimes involves banging my head against my desk until I gain some form of clarity :).  I hope my list helps others avoid this sort of frustration:

  1. Don't put "exit" in either the here doc or the sql script
    • Exit is a keyword in the shell, so using it in a here doc can cause lots of strange problems.
  2. Use tabs, not spaces
    • More than once, I've been stuck on a here doc problem only to realize that this actually makes a difference.
  3. Don't put a tab in front of the last line.
    • A lot of online tutorials show a tab in front of the last line, but it has never worked for me.
  4. Do NOT put a space after the last line in the here doc.  That will also break your script.
    • This rule probably took me the most time to discover.

Remember, if you don't follow these rules, your shell script will do very strange things.  You have been warned :)

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