eva

Run the calculator in interactive mode

$ eva

$ eva "[(1 + 2) * 2 ^ 2]"

$ eva --fix [5] "[5 / 3]"

$ eva "[sin(1) + cos(1)]"

eva <command> [options] [arguments]

Note: As a non-standard command, its exact syntax is highly dependent on the specific script implementation.

list
    Lists all installed or available Emacs versions.

install <version>
    Downloads and installs a specified Emacs version. The 'version' might be a specific tag, branch, or release identifier.

use <version>
    Switches the default Emacs executable in the user's PATH to the specified version, often by managing symlinks.

remove <version>
    Removes a specified Emacs version from the system.

current
    Displays the Emacs version currently in use.

help
    Displays usage instructions for the specific 'eva' script.

The command "eva" is
not
a standard, universally recognized Linux command found in most distributions' core utilities. If encountered, it typically refers to a custom script or a specialized project, most commonly associated with an Emacs Version Archive (EVA) tool.

In this context, eva would be a shell wrapper designed to manage multiple installations or versions of the Emacs text editor. Its primary purpose would be to simplify the process of switching between different Emacs versions (e.g., stable, development, or specific builds), installing new ones, or removing old ones, much like version managers for programming languages (e.g., `pyenv` for Python, `nvm` for Node.js).

The exact functionality, syntax, and existence of eva depend entirely on the specific implementation found on a given system, as it's not part of standard GNU/Linux tools or POSIX specifications. Users might create or install such a script to streamline their Emacs development or usage workflow.

Non-Standard Command: The "eva" command is not a standard utility found on most Linux distributions.
Its functionality, existence, and parameters are entirely dependent on how it has been implemented or installed on a particular system, often as a custom shell script or an Emacs Lisp utility with a shell wrapper.
There is no universal man eva page, and its behavior will vary wildly across different systems or user setups where it might exist.

When "eva" is encountered, it is most often a shell script (e.g., Bash or Zsh) that orchestrates the management of Emacs versions. This typically involves operations like downloading Emacs source or binaries, compiling Emacs, managing symbolic links in a user's `PATH` to point to the desired Emacs installation, and handling installation directories. It might also interact with configuration files (like `~/.emacs.d`) or package managers to ensure a consistent environment across different Emacs versions. Its exact behavior is dictated by the specific content of the script.

The concept of "eva" as an Emacs version manager likely arose from the practical need for developers and power users to easily switch between different Emacs installations or configurations without tedious manual path manipulation. It is not a project with a single, long-standing, well-documented history like `ls` or `grep`, but rather represents a pattern for custom tools developed within the Emacs community to streamline workflow. Its development is often decentralized, with various users or small groups creating their own versions of such a tool based on their specific needs and preferences.

emacs(1), pyenv(1), nvm(1), rbenv(1)