Bash script template

#!/usr/bin/env bash 
set -o errexit     # Exit on error 
set -o nounset  # Exit if variable is unset
set -o pipefail   # Exit if one side of a pipe fails

firstargument="${1:-somedefaultvalue}" 

echo "$firstargument"

Below is a script template with options.

#!/bin/bash
#
# FILNAME - SHORT DESCRIPTION
#
# (c) 2012 - DONALD DUCK <dd@disney.org> - all rights reserved
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.

# default settings
COUNT=0
unset R # Default unset
N=1     # Default set
UNIT=""
TEXT="Distance between A and B"

usage() {
        echo "usage: $0 [-mkrh] [-c count -n] [-t text]"
        echo "  -m    m flag fx. report result in miles"
        echo "  -k    k flag fx. report result in km"
        echo "  -r    r flag"
        echo "  -c    c flag with value"
        echo "  -n    n flag - unset"
        echo "  -t    t flag with text"
        echo "  -h    help"
        echo ""
        echo "  Description line1"
    echo "      Description line2"
    exit 1
}

# collect options and override default

while getopts ':c:t:mkrnh' CMDLINEARG
do
        case "${CMDLINEARG}" in
        c)
                COUNT=${OPTARG}
                ;;
        t)
                TEXT=${OPTARG}
                ;;
        m|k)
                [ ! -z "${UNIT}" ] && echo '-m and -k are mutually exclusive. Select miles or km.'\
                        && usage
                UNIT="${CMDLINEARG}"
                ;;
        r)
                R=${CMDLINEARG}
                ;;
        n)
                N=${OPTARG}
                ;;
        h)
                usage
                ;;
        *)  echo -e "ERROR:  illegal option -${OPTARG}"
            ;;
        esac
done
echo -e "Settings"
echo -e "COUNT = $COUNT"
echo -e "TEXT  = $TEXT"
echo -e "UNIT  = $UNIT"
echo -e "R     = $R"
echo -e "N     = $N"
echo -e "Done..."

Running the script - example

heth@mars:~/bin$ ./bash_template -c 78 -t "Distance between sun and mars" -r -m
Settings
COUNT = 78
TEXT  = Distance between sun and mars
UNIT  = m
R     = r
N     = 1
Done...

Links

• getopts tutorial