coreutils: Numeric expressions

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1 16.4.2 Numeric expressions
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1 ‘expr’ supports the usual numeric operators, in order of increasing
1 precedence.  These numeric operators have lower precedence than the
1 string operators described in the previous section, and higher
1 precedence than the connectives (next section).
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1 ‘+ -’
1      Addition and subtraction.  Both arguments are converted to
1      integers; an error occurs if this cannot be done.
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1 ‘* / %’
1      Multiplication, division, remainder.  Both arguments are converted
1      to integers; an error occurs if this cannot be done.
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