how to use getopt(s) as technique for passing in argument in bash

Question

Can someone show me an example how to use getopts properly or any other technique that I would be able to pass in an argument? I am trying to write this in unix shell/bash. I am seeing there is getopt and getopts and not sure which is better to use. Eventually, I will build this out to add for more options.

In this case, I want to pass the filepath as input to the shell script and place a description in the case it wasn't entered correctly.

export TARGET_DIR="$filepath"

For example: (calling on the command line)

./mytest.sh -d /home/dev/inputfiles

Error msg or prompt for correct usage if running it this way:

./mytest.sh -d /home/dev/inputfiles/

Answer 1

As a user, I would be very annoyed with a program that gave me an error for providing a directory name with a trailing slash. You can just remove it if necessary.

A shell example with pretty complete error checking:

#!/bin/sh

usage () {
  echo "usage: $0 -d dir_name"
  echo any other helpful text
}

dirname=""
while getopts ":hd:" option; do
  case "$option" in
    d)  dirname="$OPTARG" ;;
    h)  # it's always useful to provide some help 
        usage
        exit 0 
        ;;
    :)  echo "Error: -$OPTARG requires an argument" 
        usage
        exit 1
        ;;
    ?)  echo "Error: unknown option -$OPTARG" 
        usage
        exit 1
        ;;
  esac
done    

if [ -z "$dirname" ]; then
  echo "Error: you must specify a directory name using -d"
  usage
  exit 1
fi

if [ ! -d "$dirname" ]; then
  echo "Error: the dir_name argument must be a directory
  exit 1
fi

# strip any trailing slash from the dir_name value
dirname="${dirname%/}"

For getopts documentation, look in the bash manual