5 SC2017

Joachim Ansorg edited this page 2021-11-15 11:26:27 +01:00

Table of Contents

• Increase precision by replacing a/b*c with a*c/b.
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:

Increase precision by replacing a/b*c with a*c/b.

Problematic code:

percent=$((count/total*100))

Correct code:

percent=$((count*100/total))

Rationale:

If integer division is performed before multiplication, the intermediate result will be truncated causing a loss of precision.

In this case, if count=1 and total=2, then the problematic code results in percent=0, while the correct code gives percent=50.

Exceptions:

If you want and expect truncation you can ignore this message.

ShellCheck doesn't warn when b and c are identical expressions, e.g. a/10*10, under the assumption that the intent is to rounded to the nearest 10 rather than the no-op of multiply by 1.

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