Is there are way to check that all variables declared in a bash script are being used? Something analogous to -Wall in c++?
Cheers
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That's somewhat tricky, because you can't do it statically.Oliver Charlesworth– Oliver Charlesworth2012-03-27 16:45:23 +00:00Commented Mar 27, 2012 at 16:45
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1 Answer
There's no built-in way to do this, no, and it can never be done perfectly, because of situations like these:
- Suppose the user's Bash profile exports
CLASSPATHas an environment variable. Then a Bash script might include a statement likeCLASSPATH=...
but never refer toCLASSPATH, if its only purpose in assigning toCLASSPATHis to modify the behavior of some program that uses the environment variable (such asjava). - Suppose that I create variables
aandb, and a variablecwhose value is obtained from the user and can be eitheraorb. I can then use${!c}to obtain the value of the user-specified variable; a given run of the script might never refer tob(becausecis set to'a'), but a different run of the script might do differently.
That said, you might be interested in the -u option to the set builtin. If your script contains this command:
set -u
then from that point on, it will be an error to refer to a variable or parameter that has not been set. This can help detect typos in variable-names and whatnot. This is obviously much less than what gcc -Wall does (since gcc always gives an error-message when you refer to an undeclared variable), but you may find it beneficial in the same way.
2 Comments
Eddy
Thanks, the
set -u would be useful. However, I'm looking for something that would check all declared variables are being used, not that all variables that are being used are declared. Perhaps a bash script would be able to do this?
ruakh
@Eddy: Yes, I understand what you're looking for. As I explained, there's no built-in way to do it, and it can never be done perfectly. Are you looking for an error-prone way to approximate that?
