MPE/iX Shell and Utilities Reference Manual, Vol 1

let(1) MPE/iX Shell and Utilities let(1)

NAME

let — evaluate arithmetic expressions

SYNOPSIS

let expression ...

((expression))

DESCRIPTION

let evaluates each arithmetic expression from left to right, using long integer arithmetic with

no checks for overﬂow. No output is generated; the exit status is 0 if the last expression has a

non-zero value, and 1 otherwise.

The following two lines are equivalent: the second form avoids quoting and enhances reada-

bility.

let "expression"

((expression))

The portable way to write these commands is to the

POSIX command:

: $((expression))

Expressions consist of named variables, numeric constants, and operators.

See Arithmetic Substitutions in sh(1) for syntax of expressions.

EXAMPLE

The commands

let a=7 ’b=4*2’ c=b+1

echo $a $b $c

produce

789

DIAGNOSTICS

Possible exit status values are:

0 The last argument evaluated to a non-zero value.

1 The last argument evaluated to a zero value, or the expression contained a syntax error,

or tried to divide by zero.

Messages

Because this utility is built into the

MPE/iX Shell, see the sh(1) man page for a complete list of

error messages that you may receive when using it.

Commands and Utilities 1-285