bin/myb


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#!/bin/sh
# Exit with success or failure with a given probability
self=myb

# No more than one argument
if [ "$#" -gt 1 ] ; then
    printf >&2 '%s: Unexpected arguments\n' "$self"
    exit 2
fi

# Sole accepted argument is denominator of the probability fraction, e.g. 3 is
# a probability of 1/3; defaults to 2
denom=${1:-2}

# Denominator must be positive integer (it can be one)
if [ "$((denom > 0))" -ne 1 ] ; then
    printf >&2 '%s: Illegal denominator %s\n' "$self" "$denom"
    exit 2
fi

# Perform the test; that's our exit value
test "$(rndi 1 "$denom")" -eq 1