Custom Bash Builtin - atexs

OVERVIEW

ate is Array Table Extension, which creates and uses high-performance vector indexes to elements of Bash arrays, permitting instant access to elements for reading and writing, fast sorting and searching using binary-searches for sorted tables.

FEATURES

• Bash Builtin Bash builtins can avoid the performance penalty of starting child processes, and can initiate script responses through callbacks to script functions.

• C-language Vector of Pointers Using fixed-length memory C structs containing pointers to the Bash array elements permits access to the Bash array elements by index through simple multiplication.

• Establishes a Virtual Table The pointers of the vector can simulate a table by pointing to Bash array elements at fixed increments. For example, a table whose rows contain three fields will have pointers to every third Bash array element.

• Use Bash Memory Management This is a mixed blessing. Using Bash variables and Bash arrays for the data permits Bash garbage collection to manage their lifetimes. The downside is that, without destructors, it is difficult or impossible to guarantee an orderly release of no-longer needed memory. Thus the indexes are not dynamic. That is, a table length is fixed until it is explicitely reindexed.

• Library I'm experimenting with an interface for including Bash script fragments of ate solutions and utilities into new Bash scripts. The library interface provides a list of available scriptlets, basic usage info about each scriptlet, and a system for managing includes without duplicates.

INSTALLATION

Prerequisites

Ensure you have the following:

• Bash version 4.0.0 or higher
• A C-compiler (gcc) for compiling the command
• bash_builtins development package
• git to clone, build, and statically link a few library dependencies

The development environment is Linux. I should work on any Linux distribution, and will probably work on BSD as well (I haven't tested it there yet).

Installation Steps

1. Clone the repository:

   git clone https://github.com/cjungmann/ate.git

2. Navigate to the cloned directory:

   cd ate

3. Run the configure script to resolve dependencies and prepare the Makefile.

   ./configure

4. Build and install the builtin:

   make
   sudo make install

5. Verify the installation by running:

   enable ate
   ate list_actions

USAGE

Syntax

ate [action_name] [handle_name] [options]

Example

The following example will make and display an ate two-column table of file names and sizes:

enable ate
source <( ate_sources ate_exit_on_error ate_print_formatted_table )

# Make a two-field table
declare AHANDLE
ate declare AHANDLE 2
ate_exit_on_error

declare name
while IFS='|' read -r -a row; do
   ate append_data AHANDLE "${row[@]}"
done < <( stat -c"%n|%s" * )

ate index_rows AHANDLE
ate_exit_on_error

ate_print_formatted_table AHANDLE