Bash script to parse command line arguments.

To use argparse.sh, source it in your script then let it parse command line arguments for you. Let's say you are writing a script, process_file.sh, and it is called with some arguments:

./process_file.sh input-data.txt -v --delimiter=',' --expression='$1, $2'

Or more succinctly:

./process_file.sh -vd, -e'$1, $2' input-data.txt

This is how argument parsing would be configured in your script to use argparse.sh:

#!/bin/bash

source "$(dirname "$0")/argparse.sh"

# Set default value.
ARG_DELIMITER=','

arg_help       "[This script is for processing a text file]"
arg_positional "[input-file]     [Input text file to process]"
arg_boolean    "[verbose]    [v] [Print information about operations being performed]"
arg_optional   "[delimiter]  [d] [Input file field separator. Default: '$ARG_DELIMITER']"
arg_optional   "[expression] [e] [Expression passed directly to \`awk '{print ...}'\`]"
parse_args

echo $ARG_INPUT_FILE
# => input-data.txt

echo $ARG_DELIMITER
# => ,

echo $ARG_VERBOSE
# => true

if [ -n "$ARG_VERBOSE" ]; then
  echo 'Beginning processing...'
fi

awk -F "$ARG_DELIMITER" "{print $ARG_EXPRESSION}" "$ARG_INPUT_FILE"

To get a better idea of the usage in a real shell script, look at advanced-usage-example.sh. The script may be called like this (note that some default values are defined):

./advanced-usage-example.sh -fp2020 infile.txt -n2 --verbose outfile.txt --outputs 3 -n 4

ARG_INFILE:             infile.txt
ARG_OUTFILE:            outfile.txt
ARG_PORT_NUMBER:        2020
ARG_OUTPUTS:            3
ARG_VERBOSE:            true
ARG_F:                  true
ARG_DELIMITER:
ARG_VERSION:
ARG_PERCENTAGE:         100%
ARG_NUMBERS:            2 4
ARG_HOST:
ARG_CHECKS:
ARG_PERL_REGEX_PATTERN: /[[:alnum:]]/
ARG_QUIET:

The recommended installation is to include argparse.sh in your $PATH. Do not make it executable as this is not necessary and not supported. Then, from any script you write on your filesystem, you may do:

#!/bin/bash

source "argparse.sh"

arg_help "[This is the help option.]"
parse_args

Another installation option is to include argparse.sh in the same directory in your script as is done in Usage.

• The parse_args function needs to be ran last after all the other functions in argparse.sh have been called. This is so that it will know all the possible arguments.

• Passing invalid arguments to the user script results in unexpected behavior from argparse.sh.

Bash >= 3.0

All parameters passed to any function in argparse.sh must be surrounded by square brackets, as done in Usage.

Functions for parsing arguments:

• arg_positional
  • Arguments:
    • arg_name
    • arg_description
• arg_optional
  • Arguments:
    • arg_name
    • arg_flag
    • arg_description
• arg_boolean
  • Arguments:
    • arg_name
    • arg_flag
    • arg_description
• arg_array
  • Arguments:
    • arg_name
    • arg_flag
    • arg_description
• arg_help
  • Arguments:
    • arg_description
• parse_args
  • Arguments:
    • None

Set HELP_WIDTH (before calling parse_args) to set the column width of the help message.

Additional helper functions and variables:

• $__DIR__
  • Full path of the directory which contains the script.
• $__FILE__
  • Full path of the script.
• ${POSITIONAL[@]}
  • Array of additional positional arguments not parsed by argparse.sh
• print_help
  • Function to print the help page, automatically done if -h flag is present
• bprint
  • Function to print the text as bold, without a trailing newline
• cprint
  • Function to print the text as 8-bit color, without a trailing newline