paraglade / rerun

Core rerun. See also http://github.com/rerun-modules

NAME

rerun - a modular shell automation framework to organize your keeper scripts.

SYNOPSYS

rerun [-h][-v][-V] [-M <dir>] [module:[command [options]]]

DESCRIPTION

Rerun is a simple command runner that turns loose shell scripts into modular automation. Rerun will help you organize your scripts into well defined command interfaces. Collections of management modules can be archived and delivered as a single executable to facilitate team hand offs. Using the "stubbs" module, rerun will even facilitate documentation and unit tests. When users execute rerun module commands, rerun can record execution data into log files.

Rerun provides two modes of operation:

1. Listing: Rerun lists modules and commands. Listing information includes name, description and command line usage syntax.
2. Execution: Rerun provides option processing (possibly defaulting unspecified arguments) and executes a script for the specified module command.

For the module developer, rerun is a trivial framework following simple conventions that easily fit in a shell environment. Rerun includes a module development tool called "stubbs" that helps create and evolve rerun modules. Stubbs contains commands to automate option processing code, metadata definition and unit testing.

Internally, rerun implements a simple dispatching mechanism to look up named commands and execute them. Commands are logically named and have a corresponding script.

Commands reside in a module and can have named parameters called options. Each option is named, described and can also be defined to use a default value or say whether it is required or not.

Rerun modules can also declare metadata describing name, description and other aspects of each command. Rerun makes use of this metadata to support a listing mode, a feature where modules and command usage are summarized for end users.

See the project wiki for additional documentation including:

• Getting started
• Installation
• Stubbs module tool
• Why rerun?

OPTIONS

-h : Print help and usage then exit.

-M DIRECTORY : Module library directory path.

-v : Execute command in verbose mode.

-V : Execute rerun and command in verbose mode.

USING

Help

For command line syntax and example usage execute rerun using the --help flag:

$ ./rerun --help
 _ __ ___ _ __ _   _ _ __
| '__/ _ \ '__| | | | '_ \ 
| | |  __/ |  | |_| | | | |
|_|  \___|_|   \__,_|_| |_|
Version: 1.0.2. License: Apache 2.0.

Usage: rerun [-h][-v][-V] [-M <dir>] [module:[command [options]]]

Listing

Without arguments, rerun will list existing modules and their description and version:

$ rerun
  stubbs: "Simple rerun module builder" - 1.0.2

To list the commands available in a module specify the module name too. Here the commands are listed for the 'stubbs' module:

$ rerun stubbs
 add-command: "add command to module"
     --command|-c <>: "the command name"
     --description <>: "the brief description"
     --module|-m <>: "the module name"
    [ --overwrite <false>]: "should overwrite?"
 add-module: "add a new module"
     --description <>: "the brief description"
     --module|-m <>: "the module name"
    [ --template <>]: "the template name or path"
    .
    . 
    .

The command listing includes the command description and any options assigned to the command.

Options that declare a default value are shown with a string between the "<>" characters.

For example, notice how "--overwrite" option shows <false>. The "false" is the default value assigned to the "--overwrite" option.

See the "Environment" section below to learn about the RERUN_MODULES environment variable. This variable specifies the directory where rerun modules exist.

Bash completion

If you are a Bash shell user, be sure to source the bash_completion.sh file. It provides listing via the tab key.

Type rerun and then the tab key. The shell will generate a list of existing modules.

$ rerun[TAB][TAB]
stubbs: 

Rerun shows the module "stubbs".

Typing the s character and the tab key again will show the commands inside the "stubbs" module:

$ rerun stubbs: [TAB]
add-command  add-module  add-option  archive  docs  edit  migrate  rm-option  test

Several commands are listed. Press tab again and choose a command. You can specify the first few characters and the command name will be completed, too.

After accepting a command, typing the tab key will list the command options.

$ rerun stubbs: add-module -[TAB]
--description  --module  --template

The stubbs:add-module command accepts three options (--description <> --module <> --template <>).

You can continue using command completion to cycle through the remaining options.

Command execution

Commands are executed by stating the module, command and any command options. The basic usage form is "rerun module:command [ options ]".

To run the "archive" command in the stubbs module, type:

$ rerun stubbs:archive
Wrote self extracting archive script: /tmp/rerun.bin

Command options are passed after the "module:command" string. Run the "stubbs:archive" command but specify where the archive file is written.

$ rerun stubbs:archive --modules waitfor --file $HOME/rerun.bin

If the 'stubbs' module is stored in /var/rerun, then the command usage would be:

$ rerun -M /var/rerun stubbs:archive

Archives

An archive contains all the rerun modules you need (you might have a library of them) and gives you the same exact interface as rerun,... all in one file!

Specifically, an archive is a set of modules and rerun itself packaged into a self extracting script (by default in a file named "rerun.bin"). Archives can be useful if you want to share a single self contained executable that contains all the needed modules.

Run an archive script like you would run rerun.

You can execute an archive via bash like so:

$ bash rerun.bin <module>:<command> --your options

If the execute bit is set, invoke the archive directly.

Here the archive is executed without arguments which causes the archive to list the modules contained within it.

$ ./rerun.bin
  waitfor: "utility commands that wait for a condition."
  .
  . listing output ommitted

Note, ".bin" is just a suffix naming convention for a self-extracting script. The archive file can be named anything you wish.

Run the waitfor:ping command in the archive:

$ ./rerun.bin waitfor:ping --server remoteserver

Archive special options

Shell archives can be executed using special parameters of its own. Below is a list of these optional arguments:

• --archive-version-release: Print the archive version and release info and exit.
• --extract-only|-N <>: Extract the archive to the specified directory and exit.
• --extract-dir|-D <>: Extract the archive to the specified directory and then execute the specified command. By default, the TMPDIR environment variable is used to create a directory to extract the archive.

See stubbs:archive for further information about creating and understanding rerun archives.

MODULES

Layout

A rerun module assumes the following structure:

<MODULE>
|-- commands
|-- `-- cmdA (directory for cmdA files)
|--     |-- metadata (command metadata)
|--     |-- options.sh (option parsing script)
|--     `-- script (command script)
|-- lib
|-- `-- functions.sh (module function library)
|-- metadata (module metadata)
|-- options (module options)
|   `-- optyY ("optY" option)
|       `-- metadata (declares metadata for "optY" option)
`-- tests
    `-- cmdA-1-test.sh (unit tests for cmdA)

Command Scripts

Rerun's internal dispatch logic uses the directory layout described above to find and execute scripts for each command.

Rerun expects an implementation script for each command.

• script: Script implementation.
• options.sh: Script to parse options (generated by stubbs for "bash" modules).

Metadata

The metadata file format uses line separated KEY=value pairs to define module attributes. The module metadata file declares two properties:

• NAME: Declare name displayed to user.
• DESCRIPTION: Brief explanation of use.

For example, a module named waitfor is declared in a file called RERUN_MODULES/waitfor/metadata:

NAME="waitfor"
DESCRIPTION="utility commands that wait for a condition."

Command metadata is described in a file called RERUN_MODULES/<module>/commands/<command>/metadata. It uses NAME and DESCRIPTION properties like a module but adds, OPTIONS.

• OPTIONS: List of options assigned to the command.

Here's the command metadata for the "ping" command:

NAME="ping"
DESCRIPTION="wait for ping response from a host"
OPTIONS="host interval"

Each command can have options assigned to it. The example above shows that the "ping" command has options called "host" and "interval".

Options are described in their own metadata files following the naming convention: RERUN_MODULES/<module>/options/<option>/metadata. Beyond just NAME and DESCRIPTION, options can also declare:

• ARGUMENTS: Does the option take an argument.
• REQUIRED: Is the option required.
• DEFAULT: Sensible value for an option default

Here's the metadata describing an option named "host":

NAME=host
DESCRIPTION="the server to reach"
ARGUMENTS=true
REQUIRED=true
DEFAULT=

Combining the examples above into the layout described earlier the "waitfor" module along with its command "ping" are illustrated here:

modules/waitfor/
|-- commands
|   `-- ping
|       |-- metadata
|       |-- options.sh
|       `-- script
|-- lib
|   `-- functions.sh
|-- metadata
|-- options
|   |-- jumps
|   |   `-- metadata
|   `-- subject
|       `-- metadata
`-- tests
    `-- ping-1-test.sh

ENVIRONMENT

RERUN_MODULES : Path to directory containing rerun modules. If RERUN_MODULES is not set, it is defaulted relative to the location of the rerun executable.

RERUN_COLOR : Set 'true' if you want ANSI text effects. Makes labels in text to print bold in the console. Syntax errors will also print bold.

VERSIONING

Rerun and its modules following the Semantic Versioning Specification. As a consequence, any backwards incompatible change to Rerun will result in its major version number being incremented. Module developers are expected to provide a version of their module compatible with each major version of Rerun.

SEE ALSO

To create modules, see stubbs.

ERROR CODE

0 : All commands executed successfully.

1 : One or more commands failed.

2 : Option syntax error.

127 : Unknown error case.

LICENSE

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

The rerun source code and all documentation may be downloaded from https://github.com/rerun/rerun/.