how to add a custom option to the mkdir command

Question

I have created lots of directories and I would to make my life lazy and to auto cd into the directory that I made with the option of -g with the result of mkdir -g foo

The terminal would be like this:

User:/$ mkdir -g foo
User:/foo/$ 

I have looked at this page but with no success.

Is there a one-liner that allows me to create a directory and move into it at the same time?

I have tried in my .bash_profile with this command, but it just overrides the command entirely. (and realizing that it is an infinite loop later)

mkdir() {
 if "$1" -eq "-g"
  mkdir "$2"
  cd "$2"
 else
  ## do the regular code
 fi
}

The other thing is that I don't want to make more aliases because I will eventually forget all of the aliases that I have.

So not I don't want this:

the command entirely. (and realizing that it is an infinite loop later)

mkcd() {
 if "$1" -eq "-g"
  mkdir "$2"
  cd "$2"
 else
  ## do the regular code
 fi
}

I know that I most likely don't have the option thingy right, please correct me on that, but any help would be awesome!

Answer 1

Use the command builtin to call an external command, bypassing any function of the same name. Also:

• What follows if is an ordinary command. To perform a string comparison, invoke the test built-in, or the [ builtin with the same syntax plus a final ], or the [[ … ]] construct which has a more relaxed syntax. See using single or double bracket - bash for more information.
• The -eq operator is for comparing integers. Use = to compare strings.
• I added some limited support for passing multiple arguments (including options such as -p). Below I call cd only if mkdir succeeded, and I call it on the last argument passed to the function.
• -g will only be recognized as the very first argument. Parsing options to locate and remove it from whatever position it's in is possible, but harder.

mkdir () {
  local do_cd=
  if [ "$1" = "-g"]; then
    do_cd=1
    shift
  fi
  command mkdir "$@" &&
  if [ -n "$do_cd" ]; then
    eval "cd \"\${$#}\""
  fi
}

I don't recommend defining your custom options. They won't be shown in --help or man pages. They aren't more memorable than defining a command with a different name: either you don't remember that you have them, and there's no advantage compared to a command with a different name, or you don't remember that they're custom, and then you can find this out immediately with a custom name by asking the shell whether it's a built-in command or function (type mkcd), which is not the case with a custom option. There are use cases for overriding a standard command, but this is not one.