Definite's Extractor

My findings on Life, Linux, Open Source, and so on.

Do not do the math with expr

expr EXPERSSION returns 1 when the EXPERSSION is empty or 0.  Thus, you cannot really use it to do arithmetic.

For example, you may find your script doing  expr 1 - 1  returns as error.

To be fair, man page expr actually mentions this. However, instead of a dedicate section EXIT STATUSES, it is hidden in the second last paragraph of DESCRIPTION.

So do yourself a favour, use BASH arithmetic like $((var+1)).

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