Core rerun

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rerun - a simple command runner because it's easy to forget standard operating procedure.


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


Rerun is a simple command runner that turns loose shell scripts into modular automation. Rerun will help you organize your implementation 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 developing modules using a test-driven development practice.

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:


-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.

--version : Print the rerun version.



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

$ ./rerun --help
 _ __ ___ _ __ _   _ _ __
| '__/ _ \ '__| | | | '_ \ 
| | |  __/ |  | |_| | | | |
|_|  \___|_|   \__,_|_| |_|
Version: v0.1. License: Apache 2.0.

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

| $ rerun 
| => List all modules.
| $ rerun freddy
| => List all freddy commands.
| $ rerun freddy:dance --jumps 3
| => Execute the freddy:dance command.
| $ rerun -M /var/rerun freddy:dance
| => Execute the freddy:dance command found in /var/rerun


Without arguments, rerun will list existing modules:

$ rerun
  freddy: "A dancer in a red beret and matching suspenders"

To list the commands available from the 'freddy' module run:

$ rerun freddy
 study: "tell freddy to study" 
   --subject <math>: "the summer school subject"
 dance: "tell freddy to dance"
   --jumps <1>: "jump #num times"

The listing consists of info about command options including default values if they were described with option metadata.

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

For example, notice how "--jumps" option shows <1>. The "1" is the default value assigned to the "--jumps" 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 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]

Rerun shows there is a module named "freddy" installed.

Typing the tab key again will show the commands inside the "freddy" module:

$ rerun freddy: [TAB]
dance  study     

In this case, two commands are found and listed. Press tab again and choose a command. After accepting a command, typing the tab key will show arguments.

$ rerun freddy:study -[TAB]

The freddy:study command accepts one option (--subject <>).

Command execution

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

To run the "study" command in the freddy module, type:

$ rerun freddy:study
studying (math)

The outputed string "studying (math)" is the printed result. In this example, "math" is the subject option's default value as defined in the module metadata.

Command options are passed after the "module:command" string. Tell freddy to study the subject, "biology" by specifying the --subject <> option:

$ rerun freddy:study --subject biology
studying (biology)

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

$ rerun -M /var/rerun freddy:study
studying (math)


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
  freddy: "A dancer in a red beret and matching suspenders" - 1.0.0
  . 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 freddy:dance command in the archive:

$ ./rerun.bin freddy:dance --jumps 3
jumps (3)

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



A rerun module assumes the following structure:

├── commands
│   ├── cmdA (directory for cmdA files)
│   │   ├── metadata (command metadata)
│   │   ├── script (command script)
│   │   └── (option parsing script)
│   └── cmdB
│       ├── metadata
│       ├── script 
│       └──
├── metadata (module metadata)
└── lib

Command Scripts

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


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

For example, a module named freddy is named and described in a file called RERUN_MODULES/freddy/metadata:

DESCRIPTION="A dancer in a red beret and matching suspenders"

Command metadata is described in a file called RERUN_MODULES/<module>/commands/<command>/metadata. Here's the command metadata for the "study" command:

DESCRIPTION="tell freddy to study"

Options are described in a file called RERUN_MODULES/<module>/commands/<command>/<option>.option. Beyond just NAME and DESCRIPTION, options can also declare:

Here's subject.option describing an option named "subject":

DESCRIPTION="the summer school subject"

Combining the examples above into the layout described earlier the "freddy" module along with its commands "dance" and "study" are illustrated here:

├── commands
│   └── dance (directory for dance command files)
│       ├── metadata (command metadata)
│       ├── (option parsing script)
│       └── script (command script)
├── lib
│   └── (module function library)
├── metadata (module metadata)
├── options (module options)
│   └── jumps ("jumps" command option)
│       └── metadata (declares metadata for "jumps" option)
└── tests
    └── (unit tests for dance)


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.


To create modules, see stubbs.


0 : All commands executed successfully

1 : One or more commands failed

127 : Unknown error case


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

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

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