bash-completion.el defines dynamic completion hooks for shell-mode and shell-command prompts that are based on bash completion.
Bash completion for emacs:
- is aware of bash builtins, aliases and functions
- does file expansion inside of colon-separated variables and after redirections (> or <)
- escapes special characters when expanding file names
- is configurable through programmable bash completion
When the first completion is requested in shell model or a shell command, bash-completion.el starts a separate bash process. Bash-completion.el then uses this process to do the actual completion and includes it into Emacs completion suggestions.
A simpler and more complete alternative to bash-completion.el is to run a bash shell in a buffer in term mode(M-x `ansi-term'). Unfortunately, many Emacs editing features are not available when running in term mode. Also, term mode is not available in shell-command prompts.
Bash completion can also be run programatically, outside of a shell-mode command, by calling `bash-completion-dynamic-complete-nocomint'
copy bash-completion.el into a directory that's on Emacs load-path
add this into your .emacs file:
(autoload 'bash-completion-dynamic-complete "bash-completion" "BASH completion hook") (add-hook 'shell-dynamic-complete-functions 'bash-completion-dynamic-complete)
or simpler, but forces you to load this file at startup:
(require 'bash-completion) (bash-completion-setup)
- reload your .emacs (M-x `eval-buffer') or restart
Once this is done, use as usual to do dynamic completion from shell mode or a shell command minibuffer, such as the one started for M-x `compile'. Note that the first completion is slow, as emacs launches a new bash process.
You'll get better results if you turn on programmable bash completion. On Ubuntu, this means running:
sudo apt-get install bash-completion
and then adding this to your .bashrc:
Right after enabling programmable bash completion, and whenever you make changes to you .bashrc, call `bash-completion-reset' to make sure bash completion takes your new settings into account.
Loading /etc/bash_completion often takes time, and is not necessary in shell mode, since completion is done by a separate process, not the process shell-mode process.
To turn off bash completion when running from emacs but keep it on for processes started by bash-completion.el, add this to your .bashrc:
if [[ ( -z "$INSIDE_EMACS" || "$EMACS_BASH_COMPLETE" = "t" ) &&\ -f /etc/bash_completion ]]; then . /etc/bash_completion fi
Emacs sets the environment variable INSIDE_EMACS to the processes started from it. Processes started by bash-completion.el have the environment variable EMACS_BASH_COMPLETE set to t.
Using a separate process for doing the completion has several important disadvantages:
bash completion is slower than standard emacs completion
the first completion can take a long time, since a new bash process needs to be started and initialized
the separate process is not aware of any changes made to bash in the current buffer. In a standard terminal, you could do:
$ alias myalias=ls $ myal<TAB>
and bash would propose the new alias. Bash-completion.el cannot do that, as it is not aware of anything configured in the current shell. To make bash-completion.el aware of a new alias, you need to add it to .bashrc and restart the completion process using `bash-completion-reset'.
bash-completion.el is known to work with Bash 3 and 4, on Emacs, starting with version 24.1, under Linux and OSX. It does not work on XEmacs.