How to change current working directory inside command_not_found_handle

Question

I'm trying to write a not found handle in Bash that does the following:

1. If $1 exists and it's a directory, cd into it.
2. If $1 exists inside a user defined directory $DEV_DIR, `cd into it.
3. If the previous conditions don't apply, fail.

Right now I have something like this:

export DEV_DIR=/Users/federico/programacion/

function command_not_found_handle () {
    if [ -d $1 ]; then          # the dir exists in '.'
        cd $1
    else
        to=$DEV_DIR$1
        if [ -d $to ]; then
            cd $to
            echo `pwd`
        else
            echo "${1}: command not found"
        fi
    fi
}

And although it seems to be working (the echo pwd command prints the expected dir), the directory in the actual shell does not change.

I was under the impression that since this is a function inside my .bashrc the shell wouldn't fork and I could do the cd but apparently that's not working. Any tips on how to solve this would be appreciated.

Mowery

Why do you need to do this? There is most likely a better way to accomplish whatever you have in mind. – Pulmonate

I want to move between subdirs inside the directory where I keep all my projects in an easy way. Doing cd ~/prog; cd something gets a bit tiring after some time. I'd love to hear any other suggestions to doing this. – Mowery

Answer 1

I think what's going on is that the shell fork()s after setting up any redirections but before looking for commands, so command_not_found_handle can't affect the interactive shell process.

Pejoration

+1 Compare: f () { echo "$$ $BASHPID"; }; f; command_not_found_handle () { echo "$$ $BASHPID"; }; fooble (assuming you don't have anything called "fooble"). A new shell is forked. (Also, note that $SHLVL and $BASH_SUBSHELL don't vary if you include those in the functions for additional comparisons.) – Pulmonate

Answer 2

What you seem to want to do may partly possible using the autocd feature:

shopt -s autocd

From man bash:

autocd - If set, a command name that is the name of a directory is executed as if it were the argument to the cd com‐ mand. This option is only used by interactive shells.

Otherwise, just create a function that you invoke by name that performs the actions you are trying to use command_not_found_handle for.

Pulmonate

This works perfectly for directories inside . but the most important thing I want to get done is being able to move quickly to directories in other locations. I'll keep it in mind though, thanks. – Mowery

@FedericoBuiles: What about the suggestion I made in the last sentence? – Pulmonate

That'd require me to type the function name each time I want to swich (which would be effectively the same as setting up autocd). I do appreciate your effort though. – Mowery

Answer 3

I've had the very same wish and the solution that I've been using for a while was opening a new tab in gnome terminal by issuing the command gnome-terminal --tab --working-directory="$FOLDER" from inside the command_not_found handle.

But today I've come up with a solution which is not tied to a specific terminal application, but has exactly the intended behaviour.

The solution uses the PROMPT_COMMAND, which is run before each prompt. The PROMPT_COMMAND is bound to a function responsible for checking for a file related to current shell, and cd'ing into the directory specified in that file.

Then, the command_not_found_handle fills in the file when a change in directory is desired. My original command_not_found_handle also checkout a git branch if the current directory is a git repository and the name matches an existing branch. But to keep focus on answering the current question, I've stripped that part of code.

The command_not_found_handle uses find for searching for the directory matching the given name and goes only 2 levels deep in the directory tree, starting from a configured list.

The code to be added to bash_rc follows:

PROMPT_COMMAND=current_shell_cd
CD_FILE="${XDG_CACHE_HOME:-$HOME/.cache}/bash-cd/$$.cd"

current_shell_cd() {
    if [ -r "$CD_FILE" ]; then
        local CD_TARGET="$( cat "$CD_FILE" )"
        [ ! -z "$CD_TARGET" ] && cd "$CD_TARGET" 2>/dev/null
        rm "$CD_FILE"
    fi
}

command_not_found_handle () { 
    local COMMAND="$1";
    # List folders which are going to be checked
    local BASE_FOLDER_LIST=(
        "$HOME/Desenvolvimento"
        "/var/www/html"  
        "$HOME/.local/opt/"
    )
    local FOLDER=$(
        find "${BASE_FOLDER_LIST[@]}" \
             -maxdepth 2 -type d \
             -iname "$COMMAND" -print -quit )
    if [ ! -z "$FOLDER" -a -d "$FOLDER" ]
    then
        mkdir -p "$( dirname "$CD_FILE" )"
        echo "$FOLDER" > "$CD_FILE"
    else
        printf "%s: command not found\n" "$1" 1>&2
        return 127
    fi
}

Ptolemy

The answer is genius! This must be accepted answer. The solution is in PROMPT_COMMAND. – Clemmy

Related discussion – reddit.com/r/bash/comments/pkjelw/… – Clemmy

Answer 4

It won't change directies if you run this program as a script in your main shell because it creates a sub-shell when it executes. If you source the script in your current shell then it will have the desired effect.

~/wbailey> source command_not_found.sh

That said, I think the following would achieve the same result:

wesbailey@feynman:~/code_katas> cd xxx 2> /dev/null || cd ..; pwd
/Users/wesbailey

just replace the ".." with your env var defined directory and create an alias in your .bashrc file.

Priestess

That's not why it's not working. The function is defined in the current shell, but Bash forks a new shell to execute the function (which is not normally the case). – Pulmonate

The idea of defining an alias is exactly what I don't want to do. I have 82 directories inside my $DEV_DIR so I don't want to be creating a new alias for each one. – Mowery

@FedericoBuiles, he's talking about overriding cd with an alias that also tries to cd to your projects directory, not a separate alias for every entry in it. You'd maybe want to actually replace cd with a shell function, not an alias, so you could e.g. [ -d "$mydir/$1" ] before trying builtin cd to it. Also, pwd doesn't take a directory as an argument, so IDK exactly what Wes was going for. – Appendix