bash expand cd with shortcuts like zsh

Question

Is it possible in bash to expand something like

cd /u/lo/b

to

cd /usr/local/bin

?

Answer 1

I have come up with an alternative solution that does not break existing bash completion rules in other places.

The idea is to append a wildcard (asterisk) to every element of the path and invoke normal bash completion process from there. So when user types /u/lo/b<Tab> my function substitutes that with /u*/lo*/b* and invokes bash completion as usual.

To enable the described behavior source this file from your ~/.bashrc. Supported features are:

• Special characters in completed path are automatically escaped if present
• Tilde expressions are properly expanded (as per bash documentation)
• If user had started writing the path in quotes, no character escaping is applied. Instead the quote is closed with a matching character after expanding the path.
• If bash-completion package is already in use, this code will safely override its _filedir function. No extra configuration is required.

Watch a demo screencast to see this feature in action:

Full code listing below (you should check the GitHub repo for latest updates though):

#!/usr/bin/env bash
#
# Zsh-like expansion of incomplete file paths for Bash.
# Source this file from your ~/.bashrc to enable the described behavior.
#
# Example: `/u/s/a<Tab>` will be expanded into `/usr/share/applications`
#


# Copyright 2018 Vitaly Potyarkin
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.




#
# Take a single incomplete path and fill it with wildcards
# e.g. /u/s/app/ -> /u*/s*/app*
#
_put_wildcards_into_path() {
    local PROCESSED TILDE_EXPANSION
    PROCESSED=$( \
        echo "$@" | \
        sed \
            -e 's:\([^\*\~]\)/:\1*/:g' \
            -e 's:\([^\/\*]\)$:\1*:g' \
            -e 's:\/$::g' \
            -e 's:^\(\~[^\/]*\)\*\/:\1/:' \
            -Ee 's:(\.+)\*/:\1/:g' \
    )
    eval "TILDE_EXPANSION=$(printf '%q' "$PROCESSED"|sed -e 's:^\\\~:~:g')"
    echo "$TILDE_EXPANSION"
}


#
# Bash completion function for expanding partial paths
#
# This is a generic worker. It accepts 'file' or 'directory' as the first
# argument to specify desired completion behavior
#
_complete_partial() {
    local WILDCARDS ACTION LINE OPTION INPUT UNQUOTED_INPUT QUOTE

    ACTION="$1"
    if [[ "_$1" == "_-d" ]]
    then  # _filedir compatibility
        ACTION="directory"
    fi
    INPUT="${COMP_WORDS[$COMP_CWORD]}"

    # Detect and strip opened quotes
    if [[ "${INPUT:0:1}" == "'" || "${INPUT:0:1}" == '"' ]]
    then
        QUOTE="${INPUT:0:1}"
        INPUT="${INPUT:1}"
    else
        QUOTE=""
    fi

    # Add wildcards to each path element
    WILDCARDS=$(_put_wildcards_into_path "$INPUT")

    # Collect completion options
    COMPREPLY=()
    while read -r -d $'\n' LINE
    do
        if [[ "_$ACTION" == "_directory" && ! -d "$LINE" ]]
        then  # skip non-directory paths when looking for directory
            continue
        fi
        if [[ -z "$LINE" ]]
        then  # skip empty suggestions
            continue
        fi
        if [[ -z "$QUOTE"  ]]
        then  # escape special characters unless user has opened a quote
            LINE=$(printf "%q" "$LINE")
        fi
        COMPREPLY+=("$LINE")
    done <<< $(compgen -G "$WILDCARDS" "$WILDCARDS" 2>/dev/null)
    return 0  # do not clutter $? value (last exit code)
}


# Wrappers
_complete_partial_dir() { _complete_partial directory; }
_complete_partial_file() { _complete_partial file; }

# Enable enhanced completion
complete -o bashdefault -o default -o nospace -D -F _complete_partial_file

# Optional. Make sure `cd` is autocompleted only with directories
complete -o bashdefault -o default -o nospace -F _complete_partial_dir cd

# Override bash-completion's _filedir (if it's in use)
# https://salsa.debian.org/debian/bash-completion
_filedir_original_code=$(declare -f _filedir|tail -n+2)
if [[ ! -z "$_filedir_original_code" ]]
then
    eval "_filedir_original() $_filedir_original_code"
    _filedir() {
        _filedir_original "$@"
        _complete_partial "$@"
    }
fi

# Readline configuration for better user experience
bind 'TAB:menu-complete'
bind 'set colored-completion-prefix on'
bind 'set colored-stats on'
bind 'set completion-ignore-case on'
bind 'set menu-complete-display-prefix on'
bind 'set show-all-if-ambiguous on'
bind 'set show-all-if-unmodified on'

Answer 2

Sorry I couldn't post earlier, I was held at work, and the bind function was more issue-prone than I first thought.

Here is what I came up with :

Bind the following script :

#!/bin/bash
#$HOME/.bashrc.d/autocomplete.sh
autocomplete_wrapper() {
    BASE="${READLINE_LINE% *} "           #we save the line except for the last argument
    [[ "$BASE" == "$READLINE_LINE " ]] && BASE="";  #if the line has only 1 argument, we set the BASE to blank
    EXPANSION=($(autocomplete "${READLINE_LINE##* }"))
    [[ ${#EXPANSION[@]} -gt 1 ]] && echo "${EXPANSION[@]:1}"  #if there is more than 1 match, we echo them
    READLINE_LINE="$BASE${EXPANSION[0]}"  #the current line is now the base + the 1st element
    READLINE_POINT=${#READLINE_LINE}      #we move our cursor at the end of the current line
}

autocomplete() {
    LAST_CMD="$1"
    #Special starting character expansion for '~', './' and '/'
    [[ "${LAST_CMD:0:1}" == "~" ]] && LAST_CMD="$HOME${LAST_CMD:1}"
    S=1; [[ "${LAST_CMD:0:1}" == "/" || "${LAST_CMD:0:2}" == "./" ]] && S=2; #we don't expand those

    #we do the path expansion of the last argument here by adding a * before each /
    EXPANSION=($(echo "$LAST_CMD*" | sed s:/:*/:"$S"g))

    if [[ ! -e "${EXPANSION[0]}" ]];then #if the path cannot be expanded, we don't change the output
        echo "$LAST_CMD"
    elif [[ "${#EXPANSION[@]}" -eq 1 ]];then #else if there is only one match, we output it
        echo "${EXPANSION[0]}"
    else
        #else we expand the path as much as possible and return all the possible results
        while [[ $l -le "${#EXPANSION[0]}" ]]; do
            for i in "${EXPANSION[@]}"; do
                if [[ "${EXPANSION[0]:$l:1}" != "${i:$l:1}" ]]; then
                    CTRL_LOOP=1
                    break
                fi
            done
            [[ $CTRL_LOOP -eq 1 ]] && break
            ((l++))
        done
        #we add the partial solution at the beggining of the array of solutions
        echo "${EXPANSION[0]:0:$l} ${EXPANSION[@]}"
    fi
}

with the following command :

    source "$HOME/.bashrc.d/autocomplete.sh" 
    bind -x '"\t" : autocomplete_wrapper'

Output :

>$ cd /u/lo/b<TAB>
>$ cd /usr/local/bin


>$ cd /u/l<TAB>
/usr/local /usr/lib
>$ cd /usr/l

The bind line could be added to your ~/.bashrc file, doing something like this :

if [[ -s "$HOME/.bashrc.d/autocomplete.sh" ]]; then
    source "$HOME/.bashrc.d/autocomplete.sh" 
    bind -x '"\t" : autocomplete_wrapper'
fi

(taken from this answer)

Furthermore, I would strongly advise against binding this command to your Tab key as it would override the default autocomplete.

Note: In some cases, this will misbehave, for isntance if you try to autocomplete "/path/with spaces/something", as the last argument to complete is determined by ${READLINE_LINE##* }. If this is an issue in your case, you should code a function that returns the last argument of a line when considering quotes

Feel free to ask for further clarification, and I welcome any suggestion to improve this script