linux compgen cmnd options.md

The compgen command in Linux is a shell built-in used primarily for generating possible completions for commands, functions, files, or other shell elements. It is part of the Bash shell and is often utilized in scripts for tab-completion or command suggestion mechanisms.

Syntax:

compgen [option] [word]

Key Features:

• The compgen command does not execute commands; instead, it outputs possible completions for the given input.
• If no options or word is provided, it lists all available completions (commands, functions, aliases, etc.).

Common Options:

Here are the most commonly used options with compgen:

Option	Description
-A alias	Lists all aliases.
-A arrayvar	Lists all array variables.
-A binding	Lists all key bindings.
-A builtin	Lists all shell built-in commands.
-A command	Lists all executable commands in the PATH.
-A directory	Lists directories in the current working directory or specified path.
-A file	Lists files in the current working directory or specified path.
-A function	Lists all shell functions.
-A group	Lists all groups.
-A helptopic	Lists all help topics.
-A hostname	Lists all hostnames.
-A job	Lists all active jobs.
-A keyword	Lists all shell keywords (reserved words).
-A running	Lists processes currently running.
-A service	Lists services known to the system.
-A setopt	Lists valid shell options that can be set with set.
-A shopt	Lists valid shell options that can be set with shopt.
-A signal	Lists all valid POSIX signals.
-A user	Lists all users on the system.

Examples:

1. List all commands in the PATH:

   compgen -A command

2. List all aliases:

   compgen -A alias

3. List all files and directories starting with "my":

   compgen -A file my

4. List all shell built-ins:

   compgen -A builtin

5. List all functions:

   compgen -A function

6. Autocomplete suggestion for a partially typed command (e.g., "ls"):

   compgen -c ls

   The -c flag matches commands that begin with the specified string.

Notes:

• compgen is a low-level utility and is often used in combination with other scripts or tools like complete for creating custom tab-completion rules.
• To see the full list of options supported by your specific shell version, refer to the Bash manual or use help compgen.