error

#!/usr/bin/env bash
# error -- Show error message
#
# $ error MSG [MSG_NEXT_LINE]...
# Displays the given messages to stderr and exits with 1.
#
# Colored output can be controled by a switch in environment:
# $ export DEEPDIVE_COLOR=auto   # by default, uses color only for tty output
# $ export DEEPDIVE_COLOR=false  # disables colored messages in tty
# $ export DEEPDIVE_COLOR=true   # forces color coded output
# $ error ...
##
# Author: Jaeho Shin <netj@ropas.snu.ac.kr>
# Created: 2010-07-28

# use prefix and a log file when specified
: ${DEEPDIVE_ERROR_PREFIX:=} ${DEEPDIVE_LOGERROR:=}
# whether to use colored output
: ${DEEPDIVE_COLOR:=auto}
auto() { [[ -t 2 ]]; }

before= after=
if $DEEPDIVE_COLOR; then
    # TODO check terminal's color support
    before=a; a() { echo -ne '\033[31m'; }
     after=b; b() { echo -ne '\033[0m'; }
fi

{
$before
for msg; do
    {
        [[ -z "$DEEPDIVE_LOGERROR" ]] ||
            echo "${DEEPDIVE_ERROR_PREFIX}$msg" >>"$DEEPDIVE_LOGERROR"
    } 2>/dev/null
    echo "${DEEPDIVE_ERROR_PREFIX}$msg"
done
$after
} >&2
false