Sh args parser

This is POSIX-compliant parser for script arguments. It helps you focus on writing the script logic by separating argument parsing and basic validation.

Contents

1. Installation
2. Usage
3. Syntax conventions
4. Configuration
5. Functions
6. License

Installation

Include parser.sh content before usage. The most convenient way is to include the parser.sh file in your script using dot or source shell built-ins. It is important to note that external files are included relative to the terminal's current directory, not the script's directory. If you decide to include files using a path relative to the script, use the following approach:

script_dir="$(dirname "$(readlink -f "$0")")"
. "$script_dir/parser.sh"

This will allow you to include the parser.sh from the script's directory, regardless of where you run the script from.

Git submodule

It is convenient to include parser in your repository as a Git submodule:

git submodule add https://github.com/nikolaypronchev/sh-args-parser.git

The repository nikolaypronchev/sh-args-parser will be copied into your repository in the sh-args-parser directory:

your-repo/
├ sh-args-parser/
| ├ parser.sh
| └ ...
├ your-script.sh
└ ...

Next, include parser.sh in your script using the approach from the previous section:

# your-script.sh
script_dir="$(dirname "$(readlink -f "$0")")"
. "$script_dir/sh-args-parser/parser.sh"

It’s important to remember that submodules are not fetched by Git by default when running git clone. To clone your repository including submodules, use the command git clone --recurse-submodules.

Usage

The parser provides functions for working with arguments. They become available after passing all script arguments to the parser using _parse:

#!/usr/bin/env sh
. parser.sh

# In most cases, all script arguments are passed to _parse: $@.
_parse --foo bar baz

_is_used_option '--foo' && echo "Option 'foo' is used"
_get_option_args_count '--foo'
_get_option_arg '--foo' 2

Option 'foo' is used
2
baz

What's next?

1. Learn about the argument syntax.
2. Configure the parser to suit your needs.
3. Map commands.
4. Map options.
5. Learn about the functions for working with parsing results.

Argument Syntax Conventions

The argument syntax is based on, but does not fully comply with, the conventions used in POSIX ^{1, 2}.

General

• Commands, options, and positional arguments are separated by spaces.
• All script arguments are case-sensitive.

Commands

A command typically represents the core action performed by the script: run, build, issue, etc. If the script is designed to perform a single action, a command is generally not required.

• A script may or may not accept a command.
• If the script accepts a command, it must be the first argument.
• A command can contain Latin letters, digits, -, and _.

Positional Arguments

• Positional arguments are placed after the command, if present.
• The presence and number of positional arguments are determined by the script's logic.
• After the special argument --, all arguments are considered positional. This allows passing arguments that start with a dash and might be confused with options.

Options

Options are script parameters. Each option has at least one alias by which it can be specified in the command line. Options often have both short and long aliases, such as -h and --help.

• Short aliases start with - and consist of a single Latin letter;
• Long aliases start with -- and consist of Latin letters, digits, -, and _;
• Short aliases can be used individually or combined. For example, -b -a -r is equivalent to -bar;
• Options may have arguments. The presence and number of arguments are determined by the specific option and the script's logic.

Configuration

Configuration is done by assigning values to special keys via _set_config before using _parse.

Name	Default Value	Description
accept_command	auto	any — The script accepts a command. none — The script does not accept a command. mapped_only — The script accepts only a mapped command. auto — The script accepts a command if at least one has been mapped.
accept_options	auto	any — The script accepts any options. none — The script does not accept any options. mapped_only — The script accepts only mapped options. auto — The script accepts only mapped options if at least one has been mapped. Otherwise, it accepts any options.
default_max_positional_args		Maximum number of positional arguments. A different value can be set for each command (see _map_command).
default_min_positional_args	0	Minimum number of positional arguments. A different value can be set for each command (see _map_command).
default_positional_arg_variable		Name of the variable that will store the single positional argument. Implicitly sets _default_max_positional_args and _default_min_positional_args to 1. Command-specific values for max_args and arg_variable disables this behavior.
mapping_key_value_delimiter	=	Key-value delimiter for options mapping (see _map_option). Allowed values: = :.
mapping_values_delimiter	,	Values delimiter for options mapping (see _map_option). Allowed values: , ; | /.
option_duplicates_allowed	false	true — Multiple uses of options are allowed. false — Multiple uses of options are not allowed.
option_key_value_delimiter	' '	Option alias-args delimiter. Allowed values: ' ' = :.
option_values_delimiter	' '	Option values delimiter. Allowed values: ' ' , ; | /.
options_combination_allowed	true	true — Combining short option aliases into combinations is allowed. false — Combining short option aliases is not allowed.
options_combination_args_allowed	true	true — Passing arguments to the last option in a combination is allowed. false — Passing arguments to the last option in a combination is not allowed.
positional_args_placement	any	any — Positional arguments can be placed anywhere, including mixed with options. before_options — Positional arguments are placed before options. after_options — Positional arguments are placed after options.

Functions

• _set_config
• _parse
• Functions for command and option mapping:
  • _map_command
  • _map_option
• Functions for working with parsing results:
  • _get_command
  • _is_used_command
  • _get_positional_args
  • _get_positional_args_count
  • _get_positional_arg
  • _is_used_option
  • _get_option_args
  • _get_option_args_count
  • _get_option_arg

_set_config

Sets the configuration variables. Full list of configuration variables and expected values can be found in the Configuration section.

_set_config '_accept_command' 'any'

_parse

Parses the provided arguments. Typically, takes all command-line arguments $@ as input.

# Parser configuration, command and option mapping above

_parse $@

# Script logic below

Functions for command and option mapping

Mapping functions are used to specify the available commands and options of the script, as well as for their basic validation. Mapping functions must be used before calling _parse.

_map_command

Maps a command. Takes key-value pairs as arguments. Key and values list are separated by _mapping_key_value_delimiter.

Key	Description
name	Command name. Required key.
description	Command description. Currently not used.
min_args	Minimum number of positional arguments when using the command.
max_args	Maximum number of positional arguments when using the command.
arg_variable	Name of the variable that will store the command's positional argument. Implicitly sets min_args and max_args to 1.

_map_command \
  name=foo \
  min_args=1 \
  max_args=2

_map_option

Maps an option. Takes key-value pairs as arguments. Key and values list are separated by _mapping_key_value_delimiter. Values of the same key are separated by _mapping_values_delimiter.

Key	Description
aliases	List of option aliases. Required key.
description	Option description. Currently not used.
min_args	Minimum number of option arguments.
max_args	Maximum number of option arguments.
variable	Name of the variable that will store option's argument when the option is used. Implicitly sets min_args and max_args to 1.
required	If the required flag is present, the option will be considered mandatory.

_map_option \
  aliases=-f,--foo \
  min_args=1 \
  max_args=10 \
  required

Functions for working with parsing results

_get_command

Outputs the used command.

_accept_command=true

_parse foo bar baz

_get_command

foo

_is_used_command

Checks if the command passed as the first argument was used.

_accept_command=true

_parse foo bar baz

_is_used_command foo && echo 'Command "foo" was used'
_is_used_command bar && echo 'Command "bar" was used'

Command "foo" was used

_get_positional_args

Outputs the positional arguments separated by space. Delimiter can be changed by passing it's value as the first argument.

_parse foo bar baz
_get_positional_args
_get_positional_args "|"

foo bar baz
foo|bar|baz

_get_positional_args_count

Outputs the number of positional arguments.

_parse foo bar baz
_get_positional_args_count

3

_get_positional_arg

Outputs the positional argument at the index passed as the first argument. Indexes start from 1.

_parse foo bar baz
_get_positional_arg 3

baz

_is_used_option

Checks if the option with the alias passed as the first argument was used.

_parse foo --bar -abc

_is_used_option foo && echo 'Option "--foo" was used'
_is_used_option --bar && echo 'Option "--bar" was used'
_is_used_option bar && echo 'Option "bar" was used'
_is_used_option -c && echo 'Option "-c" was used'

Option "--bar" was used
Option "-c" was used

_get_option_args

Outputs the arguments of the option separated by space. Mandatory option alias is expected as the first argument. Delimiter can be changed by passing it's value as the second argument.

_parse -v foo bar baz
_get_option_args -v
_get_option_args -v "|"

foo bar baz
foo|bar|baz

_get_option_args_count

Outputs the number of arguments for the option with the alias passed as the first argument.

_parse -o foo bar baz

_get_option_args_count -o

3

_get_option_arg

Outputs the argument for the option with the alias passed as the first argument, at the index provided as the second argument. Indexes start from 1.

_parse -o foo bar baz

_get_option_arg -o 3

baz

TODO

• Add examples;
• Implement "Help" generation;
• Add tests.

License

This project is licensed under the terms of the MIT license.