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BaSF - Bash Scripting Framework

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basf is a minimalist framework to write command line applications under the umbrella of the basf command, organized in modules and with a simple and unique interface.

The typical invocation of basf on the command prompt is:

$ basf <module> <action> [options...]

Bootstrapping the application

The simplest way to bootstrap the application is to simply source the basf main file basf

#!/bin/bash

source /path/to/basf/basf

Modules

A module is a container that organizes a set of related commands - the actions.

From the user perspective, the call of a module and it's action is similar to call a command on the command line. But instead of grouping several related commands loosely by a similar name, a module groups this commands into the same namespace.

In addition to the actions a module provides typically other common information, such a description and a help.

Bash and therefore modules supports inheritance and each module automatically inherits from default.bsl module (it is located in the libs/ directory).

Actions

Actions are functions that can be called by the user. Or if you think OOP, then you can also say that these are the public methods of your modules.

Within a module a normal bash function is an action if it starts with the prefix do_. A action can request any parameter like every other function within the $@ variable and that works as expected. I.e. every value after <action> is passed as a parameter to the action.

There are also some predefined actions. These are:

  • usage
  • version
  • help

These actions do what they obviously should do. You can overwrite this actions but usually there is no good reason to do it.

The default implementation of these functions can be found in libs/default.bsl.

Default action

There are several ways to control the behavior when the module was called without specifying an action.

First, there is the default behavior. If nothing else works, then the function do_help is called. This function is already defined in the base file and therefore pretty sure available.

The first way to change this behavior is to set another default action using DEFAULT_ACTION as described above.

The second, not recommended, way is the most obvious - overwrite the do_help function.

A third possibility is to implement the __module function.

Fallback action

By default, an error is thrown when the requested action was not found. However, if a function __action exists, then this function is called instead.

Notice that this function is called for all unknown actions, but not if no action is specified at all. For that case look at the default action section.

Module configuration

The following variables are optional.

  • DESCRIPTION

    Description of this module. Defaults empty

  • DEFAULT_ACTION

    The default action of the module if none is given. Defaults to help

  • VERSION

    The version of this module. Defaults to 0.1.0

  • HIDDENMODULE

    Hide this module in the module overview if set to 1. Defaults to 0

Parameters

Parameters to an action are defined in the describe_<action>_parameters function.

describe_has_parameters() {
    echo "<module>"
}

Parameters are accessed via the ${@} variables.

Parameters are displayed in the help.

Extra actions:
  has <module>              Return true if the module or alias is installed, otherwise false.

Options

Options of an action are defined in the describe_<action>_options function using the make_option function.

describe_list_options() {
    make_option --name "only_names" --long "only-names" --short "n" --desc "Output names of modules only"
    make_option --name "all"        --long "all"        --short "a" --desc "Do not omit hidden modules"
}

Options are displayed in the help.

Extra actions:
  list                      List all available modules
    -n --only-names           Output names of modules only
    -a --all                  Do not omit hidden modules

Options are accessed within the the action with has_option

if has_option "only_names" $@; then
    # optional code here...
fi

Currently only flag options are supported. Options with parameters are covered in #16

Hiding actions

Sometimes it can be useful to hide actions from the help page. To hide an action define a hide_<action> function that returns a zero exit code.

Aliases

Aliases are lightweight modules that are used without actions. Aliases make use of the __module function defined in the alias.bsl library.

Aliases are defined by declaring the variables ALIAS_MODULE and ALIAS.

By inheriting the alias library the __module function and the help action are defined.

  • ALIAS_MODULE

    Defines the module the alias is a shortcut for. This is only used for the help.

  • ALIAS

    The module, action, parameters and options of the alias. Will be invoked in the __modules function.

Other module configurations like DESCRIPTION, VERSION and HIDDENMODULE are available. However, DEFAULT_ACTION cannot be used as the __module function is used.

Libraries

Libraries are used to group reusable functions. Libraries are devined in .bsl files in the library directories.

To use a library in a module load it using the inherit function.

inherit config tests output

There are several predefined libraries as described below

  • alias
  • config
  • core
  • default
  • environment
  • git
  • output
  • tests

The alias library

The alias library is used for aliases that are defined using the ALIAS_MODULE and ALIAS variables.

The config library

Library functions for working with configuration files.

  • read_config_value

    Load the value for key key from a configuration file file.

    Parameters:

    • file The file to read from
    • key The key

    Note:

    The configuration file must be a valid bash script, that is, the file must be loadable with source $file.

The core library

Core contains functions used by the basf core. The core library is not intended to be used in modules.

The default library

The default library is the 'base class' for modules. Here default actions and default module behavior is defined.

The environment library

The environment library provides functions to query the application's environment.

  • environment_platform

    Echoes the platform provided by uname. Examples are 'linux' or 'mingw64'.

  • environment_is_root

    Returns zero if the application is called with root privileges, non-zero otherwise.

The git library

Provides helpful functions related to git.

  • environment_platform
  • git_current_branch
  • git_tracking_branch
  • git_changes
  • git_has_empty_index
  • git_has_clean_stage
  • git_has_untracked_files
  • git_has_unstaged
  • git_wc_root
  • git_editor
  • git_pager

The output library

The output library provides functions for colored and structured output

Colored and highlighted lines:

  • write_bold
  • write_bold_red
  • write_norm_red
  • write_bold_green
  • write_norm_green
  • write_bold_yellow
  • write_norm_yellow
  • write_bold_blue
  • write_norm_blue
  • write_bold_magenta
  • write_norm_magenta
  • write_bold_cyan
  • write_norm_cyan
  • write_bold_white
  • write_norm_white
  • write_norm_highlight
  • write_bold_highlight

Centered blocks with a fixed width containing a fixed word. Call with any argument to add brackets:

  • write_block_done
  • write_block_ok
  • write_block_skip
  • write_block_fail

Prefixed messages:

  • write_error_msg
  • write_warning_msg
  • write_info_msgwrite_info_msg

Lists:

  • write_list_start - Write a list headline. If -p is passed, the output is forced to plain.
  • write_kv_list_entry - Write a key/value list entry with $1 on the left and $2 on the right.
  • write_numbered_list_entry

Padding:

Echo the $text with at least $count characters. If width of $text is shorter than $count characters, then the missing characters are padded by spaces.

  • lfill $text $count - pads left
  • rfill $text $count - pads right

The tests library

The tests library provides simple tests:

  • is_number

  • is_function

  • has_no_option $@

    Returns zero if the current action was called with no options, non-zero otherwise.

  • has_option <name of the option> $@

    Returns zero if the current action was called with the give option, non-zero otherwise.

Keep off the grass!

Global scope code is forbidden in modules, aliases and libraries.

Your module will be sourced for tasks other than running your actions. For example, your module will be sourced to obtain the description. Any code being run here would be a very bad thing!

Customizing

  • BASF_BINARY_FILEPATH

Specifies the filepath to the application's main file as entry points for subscripts. Defaults to ${0}. Should not be changed.

  • BASF_PROGRAM_VERSION

The Application's version. Defaults to basf's version.

  • BASF_PROGRAM_NAME

The name of the application. Defaults to basename ${BASF_BINARY_FILEPATH}

  • BASF_CUSTOM_LIB_PATH

Additional path for libs. See libs for details

  • BASF_CUSTOM_MODULE_PATH

Additional path for modules. See modules for details

  • BASF_CUSTOM_ALIASES_PATH

Additional path for aliases. See aliases for details

Directories

There are three types of directories:

  • libs - The library directories
  • modules - The module directories
  • aliases - The alias directories

All types of directories will be looked up as subdirectories of these directories in this order:

  • "${HOME}/.${BASF_PROGRAM_NAME}"
  • "${HOME}/.basf"
  • "${BASF_PROGRAM_ROOT}"
  • "${BASF_ROOT}"
  • "/usr/share/${BASF_PROGRAM_ROOT}"
  • "/usr/share/basf"
  • "/usr/local/share/${BASF_PROGRAM_ROOT}"
  • "/usr/local/share/basf"
  • "/opt/${BASF_PROGRAM_ROOT}"
  • "/opt/basf"

The modules/libs/aliases found in directories higher in the list take precedence.

Completion

BASF comes with dynamic completion (currently for bash only).

This command will create a completion script for bash:

<basf program name> completion bash

To use completion in the shell add this to .bashrc:

source <( <basf program name> completion bash)