.TH SH-EXPR 1.SH NAMEexpr, ntest, mpexpr \- shell module for simple arithmetic..SH SYNOPSIS.B load exprOR.B load mpexpr .B ${expr[-r.I radix][.I arg...].B }.br.B ntest.I num.br.SH DESCRIPTION.I Exprand.I mpexprare loadable modules for.IR sh (1)that provide support for integer arithmetic..I Expruses 64-bit signed integers;.I mpexpruses arbitrary-precision signed integers.They each provide the same interface:a command.IR ntest ,which performs a simple boolean teston its integer argument, and thesubstitution operator.IR expr ,which takes an expression in Reverse Polishnotation, and yields its result..PP.I Ntestreturns true if its argument.I numis non-zero,and false otherwise..PP.I Exprevaluates each.I argin turn; if it is an integer it gets pushed ontothe stack; otherwise it should nameone of the operators below, whereuponthe appropriate number of operands arepopped off the stack, evaluated as argumentsto the operator, and the result pushed back ontothe stack. Arguments are passed to the operatorfirst-pushed first, so, for instance,.B ${expr 2 1 -}yields 1, not -1.Alternative names are given for some operators;this is to avoid the necessity of quoting operatorsthat contain.IR sh (1)metacharacters. Integers are given in the same form acceptableto Limbo. The relational operators yield either1 (true) or 0 (false). If the.B -roption is given,.I radixspecifies an output base for printed numbers.It may be from 2 to 36;.I mpexpralso allows 64 to specify base64 notation.Numbers are printed in a form suitable for re-interpretationby.IR expr ..PPWhen all its arguments have been evaluated,.B expryields all the values remaining on its stack, first pushedfirst. Note that bitwise operators treat their operands as if theywere stored in two's complement form. The operators supported by expr are as follows (the numberof operands required in is given parentheses)..TP 15.BR + \ (2)Addition.TP.BR - \ (2)Subtraction.TP.BR x ,\  * \ (2)Multiplication.TP.BR / \ (2)Division. Division by zero raises a.B divide by zeroexception..TP.BR % \ (2)Modulus. A zero modulus will cause a.B divide by zeroexception to be raised..TP.BR and \ (2)Bitwise-and..TP.BR or \ (2)Bitwise-or..TP.BR xor \ (2)Bitwise-xor..TP.BR ~ \ (1)Bitwise-complement...TP.BR _ \ (1)Unary minus..TP.BR << ,\  shl \ (2)Shift left..TP.BR >> ,\  shr \ (2)Shift right..TP.BR = ", " == ", " eq " (2)"Equality..TP.BR != ", " neq " (2)"Inequality..TP.BR > ", " gt " (2)"Greater than..TP.BR < ", " lt " (2)"Less than..TP.BR <= ", " le " (2)"Less than or equal to..TP.BR >= ", " ge " (2)"Greater than or equal to..TP.BR ! ", " not " (1)"Logical negation..TP .BI rep \ \f1(\fPn\f1)\fP.B Reprepeats the last operation (which musthave been a two-operand operation otherthan.BR seq )until the values in the stack are exhausted..TP.BR seq \ (2).B Seqpushes on the stack a sequence of numbers rangingnumerically from its first argument up to and includingits second argument. If its second argument isless than its first, the sequence will descend..TP.BR rand \ (1)(\fImpexpr\fP only). Push a secure random number;the argument value gives the size of the number, in bits..TP.BR bits \ (1)(\fImpexpr\fP only). Push the size, in bits, of the argument..TP.BR expmod ", " invert " (2)"(\fImpexpr\fP only). See.IR keyring-ipint (2)..TP.BR exp ", " xx ", " **(\fImpexpr\fP only). Exponentiation..SH SOURCE.B /appl/cmd/sh/expr.b.SH SEE ALSO.IR sh (1),.IR sh-std (1),.IR sh-tk (1),.IR keyring-ipint (2).SH BUGSPostfix notation can be confusing.Any operators that contain shell metacharacters (e.g. ``*'', ``>'')must be quoted to avoid interpretation by the shell.Base64 notation can contain # characters, which needquoting to avoid interpretation by the shell.