Execute a bash function upon entering a directory

Question

I'd like to execute a particular bash function when I enter a new directory. Somethink like:

alias cd="cd $@ && myfunction" 

$@ doesn't work there, and adding a backslash doesn't help. I'm also a little worried about messing with cd, and it would be nice if this worked for other commands which changed directory, like pushd and popd.

Any better aliases/commands?

Answer 1

Aliases don't accept parameters. You should use a function. There's no need to execute it automatically every time a prompt is issued.

function cd () { builtin cd "$@" && myfunction; } 

The builtin keyword allows you to redefine a Bash builtin without creating a recursion. Quoting the parameter makes it work in case there are spaces in directory names.

The Bash docs say:

For almost every purpose, shell functions are preferred over aliases.

Answer 2

The easiest solution I can come up with is this

myfunction() {   if [ "$PWD" != "$MYOLDPWD" ]; then     MYOLDPWD="$PWD";     # strut yer stuff here..   fi }  export PROMPT_COMMAND=myfunction 

That ought to do it. It'll work with all commands, and will get triggered before the prompt is displayed.