expr(1) expr(1)[top]Nameexpr- evaluate expressionsSyntaxexprarg...DescriptionThe arguments are taken as an expression. After evaluation, the result is written on the standard output. Each token of the expression is a separate argument. The operators and keywords are listed below. The list is in order of increasing precedence, with equal precedence operators grouped.expr|exprYields the firstexprif it is neither null nor 0. Otherwise yields the second expr.expr&exprYields the firstexprif neitherexpris null or 0. Otherwise yields 0.exprrelopexprThe relop is one of < <= = != >= > and yields 1 if the indicated comparison is true, 0 if false. The comparison is numeric if bothexprare integers, otherwise lexicographic.expr+exprexpr -exprYields addition or subtraction of the arguments.expr*exprexpr /exprexpr %exprYields multiplication, division, or remainder of the arguments.expr:exprmatch stringexprThe matching operators and compare the string first argument with the regular expression second argu‐ ment; regular expression syntax is the same as that of The \(...\) pattern symbols can be used to select a portion of the first argument. Otherwise, the matching operator returns the number of charac‐ ters matched (0 on failure). (expr) Parentheses for grouping. To lexically compare two special characters, such as with you must pre‐ cede them with identical nonspecial characters. To lexically compare any two operators, such as with you must precede them with identical, nonoperator characters. For example:expr"X(" ">" "X)"expr"S+" |expr"S-"ExamplesThe first example adds 1 to the shell variable a: a=`expr $a + 1` The second example finds the file name part (least significant part) of the pathname stored in variable a,expr$a : ´.*/\(.*\)´ ´|´ $a Note the quoted shell metacharacters.DiagnosticsThe command returns the following exit codes: 0 The expression is neither null nor 0. 1 The expression is null or 0. 2 The expression is invalid.See Alsoed(1), sh(1), test(1) expr(1)

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