Gnu/coreutils/Numeric-expressions

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16.4.2 Numeric expressions

expr supports the usual numeric operators, in order of increasing precedence. These numeric operators have lower precedence than the string operators described in the previous section, and higher precedence than the connectives (next section).

+ -

Addition and subtraction. Both arguments are converted to integers; an error occurs if this cannot be done.

* / %

Multiplication, division, remainder. Both arguments are converted to integers; an error occurs if this cannot be done.