Find path of original command when overriding it with a shell script?

Question

I'm writing a wrapper script to wrap around the execution of another command; in this case the Chef kitchen command. My script will also be called kitchen and put earlier in $PATH so that running kitchen from bash will run my wrapper script instead.

The question is: how do I call the original version of kitchen? The obvious way, of course, is just to give the full path — just put /usr/bin/kitchen in the script, but someone else may have it installed at a different path. And of course that precludes any other wrapper scripts—it'd be nice if the solution were stackable.

Two approaches come to mind, both variants on the same theme:

1. In the script, go through $PATH. Compare each entry to $(dirname "$0") using stat using device number & inode number to see if its the same directory. If so, remove it from $PATH. Then can just call kitchen, because it shouldn't re-call the wrapper script.
2. Similar to #1, but do the $PATH lookup by hand in the script, and use stat on each result vs. $0. Keep skipping until we find ourself, then use the next one found. If we never find ourself, then just exec it normally (to handle the case the wrapper isn't in $PATH but was executed by providing a path to it)

Is there a better way? Or does code to do this already exist somewhere on a typical Debian or Ubuntu Linux system?

Answer 1

I've done something similar a few times in the past and what I'll do is just use command kitchen in the script, name it something else like my-kitchen and then create an alias:

alias kitchen=/path/to/my-kitchen

Not sure if that works for your use case though.

Answer 2

You can escape an alias with a backslash to prevent it from being expanded by the shell. command also works.

I don't have kitchen on my desktop, so I'll demonstrate by aliasing pwd to uname -r :

$ alias pwd='uname -r'
$ pwd
5.10.0-8-amd64
$ \pwd
/home/cas
$ command pwd
/home/cas
$ unalias pwd
$ pwd
/home/cas

Answer 3

It sounds like you want to execute the next kitchen in $PATH.

#!/bin/bash
me="$0" 
foundit=""
for d in $( echo "$PATH" | tr ":" " " ) ; do
  if [[ $foundit  == "" ]] ; then
    if [[ "$me" != "$d/kitchen" ]] ; then
      if [[ -x "$d/kitchen" ]] ; then
        foundit="$d/kitchen" 
      fi
    fi
  fi
done
# the next "kitchen" is in "`$foundit`"
# read `man bash`, about the `eval` and `exec` builtins