refactor: command_exists

[jeevithakannan2]

Pull Request

Title

Refactor command_exists function to use command -v instead of which

Type of Change

• [x] Refactoring

Description

command_exists function uses which, that is not POSIX-compliant that may result in error in some systems. A simple refactor to command -v solves the issue. command -v is also a POSIX-compliant built-in command.

Issue related to PR

• Resolves #https://github.com/ChrisTitusTech/linutil/issues/211

Checklist

• [x] My code adheres to the coding and style guidelines of the project.
• [x] I have performed a self-review of my own code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] My changes generate no errors/warnings/merge conflicts.