Bash script to show logging/output functions based on verbosity level

echo_functions.sh

#!/bin/bash
# see http://stackoverflow.com/a/14203146 for more on this
set -e

verbose=0

# log functions
error() { >&2 echo $*; }                            # prints to stderr always
warn() { (($verbose>0)) && echo $* || true; }       # prints when verb is >0
info() { (($verbose>1)) && echo $* || true; }       # prints when verb is >1
debug() { (($verbose>2)) && echo $* || true; }      # prints when verb is >2
verbose() { (($verbose>3)) && echo $* || true; }    # prints when verb is >3


USAGE="
usage:

    $(basename $0) [options] arg1 [arg2 ...]

options:
    -v, --verbose   increase verbosity (up to 4 v's)
    -h, --help      print this message and exit

    Simple functions using echo for use with varying verbose levels. Try adding
    more '-v' options and see how it works.
"

while [[ $1 == -* ]]; do
    case $1 in
        -v|--verbose)
            ((verbose+=1))
            # do not shift again!
            ;;
        -h|--help)
            echo "$USAGE"
            exit
            ;;
        *)
           >&2 echo "$(basename $0): unknown option $1" \
                "(run '$(basename $0) --help' for available options)"
            exit 1
    esac
    shift
done


error "This is an error message"
warn "This is a warning message"
info "This is an info message"
debug "This is a debug message"
verbose "This is a verbose message"

echo "end of script"