error_ex

#!/bin/bash
#
# An approach to return a detailed error from a function. This example
# illustrates the use of ctx.

readonly DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
. ${DIR}/../gobash


function sum() {
        # A detailed error messages can be written to context; note
        # that we can use the default context, in which case we do not
        # need to pass the first argument.
        local -r ctx="${1}"
        local -r a="${2}"
        local -r b="${3}"

        # When we detect an error, write the message to context.
        [ -z "${a}" ] && ctx_w $ctx "a was not set" && return $EC
        [ -z "${b}" ] && ctx_w $ctx "b was not set" && return $EC

        ! is_int "${a}" && ctx_w $ctx "a is not an int" && return $EC
        ! is_int "${b}" && ctx_w $ctx "b is not an int" && return $EC

        echo "${a} + ${b}" | bc
}

ctx=$(ctx_make)
# If something goes wrong, print the context.
sum "$ctx" || ctx_show $ctx
# Output:
# a was not set
# 19 sum ./error_ex
# 30 main ./error_ex

val=$(sum "$ctx" 5 10) || \
        { echo "This should never happen."; }
echo "${val}"
# Output: 15