Naruzo's blog

Exclude arbitrary directories from bash's tab completion

I got tired of `cd` (and `ls`, and `vim`, and...) always suggesting .svn directories on tab completion, so I found a way to filter them.

* Before we go any further, switching to `git` was not an option ;)

Luckily, bash's tab completion is entirely scriptable, and the out-of-the-box completions are all editable functions housed in the `/etc/bash_completion` file.

The `_filedir()` and `_filedir_xspec()` functions in /etc/bash_completion handle most (all?) directory name evaluation.

I used the stock versions of those functions to make the script below, added the `has_element`-related code.

Installation:

1. Install the bash_completion package, as necessary (on OSX: `brew install bash_completion`)
2. Save the code below to /etc/bash_completion.d/cdexclude (/usr/local/etc/bash_completion.d/cdexclude, if you're on OSX and installed using Homebrew)
3. Edit ~/.cdexclude and add any directory fragments you want to exclude from tab completion, one per line (eg, in my file I have ".svn" as one line)
4. `source /etc/bash_completion` to enable the changes

# Install bash_completion (using brew or whatnot) and shove
#   this into /usr/local/etc/bash_completion.d
#
# All the overrides below do is prevent directories that match
#   a line in your $HOME/.cdexclude from showing up in tab
#   completions.
#
# e.g. If you put ".svn" in ~/.cdexclude your subversion directories
#   won't show up in tab completion.
#
CDEXCLUDE_FILE=~/.cdexclude
CDEXCLUDE=( $( cat "$CDEXCLUDE_FILE" 2>/dev/null ) )

if [ ${#CDEXCLUDE[@]} -gt 0 ]; then
    echo "Loaded '${#CDEXCLUDE[@]}' entries from $CDEXCLUDE_FILE"
else
    echo "HAS NO ENTRIES"
fi

# Find an element in the CDEXCLUDE array
has_element() {
    local hay needle=$1
    for hay in "${CDEXCLUDE[@]}"; do
        [[ "$hay" == "$needle" ]] && echo "found" && return 0
    done
    return 1
}

_filedir()
{
    local i IFS=$'\n' xspec

    _tilde "$cur" || return 0

    local -a toks
    local quoted tmp

    _quote_readline_by_ref "$cur" quoted
    toks=( ${toks[@]-} $(
        compgen -d -- "$quoted" | {
            while read -r tmp; do
                # If the directory is in your .cdexclude file, skip it
                [[ `has_element "\`basename $tmp\`"` ]] && continue
                # TODO: I have removed a "[ -n $tmp ] &&" before 'printf ..',
                #       and everything works again. If this bug suddenly
                #       appears again (i.e. "cd /b<TAB>" becomes "cd /"),
                #       remember to check for other similar conditionals (here
                #       and _filedir_xspec()). --David
                printf '%s\n' $tmp
            done
        }
    ))

    if [[ "$1" != -d ]]; then
        # Munge xspec to contain uppercase version too
        [[ ${BASH_VERSINFO[0]} -ge 4 ]] && \
            xspec=${1:+"!*.@($1|${1^^})"} || \
            xspec=${1:+"!*.@($1|$(printf %s $1 | tr '[:lower:]' '[:upper:]'))"}
        toks=( ${toks[@]-} $( compgen -f -X "$xspec" -- $quoted) )
    fi
    [ ${#toks[@]} -ne 0 ] && _compopt_o_filenames

    COMPREPLY=( "${COMPREPLY[@]}" "${toks[@]}" )
} # _filedir()

_filedir_xspec()
{
    local IFS cur xspec

    IFS=$'\n'
    COMPREPLY=()
    _get_comp_words_by_ref cur

    _expand || return 0

    # get first exclusion compspec that matches this command
    xspec=$( awk "/^complete[ \t]+.*[ \t]${1##*/}([ \t]|\$)/ { print \$0; exit }" \
        "$BASH_COMPLETION" )
    # prune to leave nothing but the -X spec
    xspec=${xspec#*-X }
    xspec=${xspec%% *}

    local -a toks
    local tmp

    toks=( ${toks[@]-} $(
        compgen -d -- "$(quote_readline "$cur")" | {
        while read -r tmp; do
            # If the directory is in your .cdexclude file, skip it
            [[ `has_element "\`basename $tmp\`"` ]] && continue
            # see long TODO comment in _filedir() --David
            printf '%s\n' $tmp
        done
        }
        ))

    # Munge xspec to contain uppercase version too
    eval xspec="${xspec}"
    local matchop=!
    if [[ $xspec == !* ]]; then
        xspec=${xspec#!}
        matchop=@
    fi
    [[ ${BASH_VERSINFO[0]} -ge 4 ]] && \
        xspec="$matchop($xspec|${xspec^^})" || \
        xspec="$matchop($xspec|$(printf %s $xspec | tr '[:lower:]' '[:upper:]'))"

    toks=( ${toks[@]-} $(
        eval compgen -f -X "!$xspec" -- "\$(quote_readline "\$cur")" | {
        while read -r tmp; do
            # If the directory is in your .cdexclude file, skip it
            [[ `has_element "\`basename $tmp\`"` ]] && continue
            [ -n $tmp ] && printf '%s\n' $tmp
        done
        }
        ))

    [ ${#toks[@]} -ne 0 ] && _compopt_o_filenames
    COMPREPLY=( "${toks[@]}" )
}

If you know a simpler way, please leave a comment!

References:  

http://www.debian-administration.org/article/An_introduction_to_bash_completion_part_1

  via http://tldp.org/LDP/abs/html/tabexpansion.html

Customer service: template

I was encouraged to write a customer service letter in regard to a piece of software that was driving my friend mad.

Whether they send it or not is up to them, but feel free to use the following for inspiration in your own customer service endeavors:

---

Dear <Company> customer service center,

I am writing in regard to your <Product> product.

On the recommendation of a colleague I downloaded the trial version of the software for evaluation.

Unfortunately, usability left much to be desired.

In fact, after two hours of using the product I was able to accomplish only the following:

 1) Create a large box with 4 other boxes inside of it

 2) Realize that in order to select/move the top-left box, I had to move the enclosing box away every time

 3) Fall to my knees and thank <insert deity here> that I hadn't shelled out $200 for the Professional version

 4) Denounce said deity for allowing <Product> to come into existence in the first place

 5) Throw my laptop out the window of a speeding car

#5 being particularly difficult due to the fact that all of the bones in my right hand were shattered from smashing my trackpad in frustration caused by #2 above.

You would be surprised how difficult it is to drive at 140 km/h while steering with your knees and frisbee-ing a laptop over a bridge into an oncoming freight train, especially given that the sulfuric acid was still simmering away, and the piece of rebar I lanced through the device's heart in white-hot, skin-rippling fury precluded a reliance on traditional flying disc aerodynamics.

In the end, however, I feel confident that any sectors on the hard drive still containing bits of <Product> code were rendered completely unreadable, and by that I have done my small part to make the world a happier place.

I applaud your effort on <Product>. However, in the interest of truth in advertising I formally request that you preface all "Buy Now" links on your site with the text, "If you're not suicidal yet, we can help."

You may also want to consider shipping an iron mallet with each copy of <Product> to prevent the hand injuries outlined above.

Thank you, and have a pleasant day.

<insert name here>