Source not working the same way for bash as for zsh, cannot forward source commands as expected

Question

I have been using bash at work and zsh at home, different macbooks. I know very little bash or zsh scripting, so I didn't dare do the switch until I managed to get my ZSH on par with what I had at work, so that I wouldn't loose productivity.

I ended up making a .dot-files repo on github, and wanted to test everything out. It worked. But when I decided to make one final adjustment, everything broke and for the life of me, I cannot understand why.

Scenario:

I have ~/.dot-files as the root of my git repo. Then two sub folders, zsh and bash. Inside of each I have hidden files, and a config that would like to source them.

$ cd ~/.dot-files/bash/
$ ls -la
drwxr-xr-x  8 me  staff    256 May  8 13:28 .
drwxr-xr-x  7 me  staff    224 May  8 13:00 ..
-rw-r--r--  1 me  staff   1791 May  8 13:08 .alias
-rw-r--r--  1 me  staff  79837 Apr 12  2022 .git-completion.bash
-rw-r--r--  1 me  staff   1602 May  8 13:49 .git-prompt
-rw-r--r--  1 me  staff   1816 May  8 13:06 .ps1
-rw-r--r--  1 me  staff    877 May  8 13:09 .utils
-rw-r--r--  1 me  staff    142 May  8 15:20 default-config

AND

$ cd ~/.dot-files/zsh/
$ ls -la
drwxr-xr-x  7 me  staff    224 May  8 13:33 .
drwxr-xr-x  7 me  staff    224 May  8 13:00 ..
-rw-r--r--  1 me  staff   1423 May  8 12:32 .alias
-rw-r--r--  1 me  staff  18582 May  8 12:32 .git-prompt.sh
-rw-r--r--  1 me  staff   2059 May  8 12:32 .prompt
-rw-r--r--  1 me  staff    926 May  8 14:01 .zsh-git-info
-rw-r--r--  1 me  staff    143 May  8 15:02 default-config

$ cat ~/.bashrc

source ~/.dot-files/bash/default-config

$ cat ~/.dot-files/bash/default-config

source "$(dirname -- "$0")/.git-prompt"
source "$(dirname -- "$0")/.ps1"
source "$(dirname -- "$0")/.alias"
source "$(dirname -- "$0")/.utils"

This does not work

-bash: ./.git-prompt: No such file or directory
-bash: ./.ps1: No such file or directory
-bash: ./.alias: No such file or directory
-bash: ./.utils: No such file or directory

$ cat ~/.zshrc

source ~/.dot-files/zsh/default-config

$ cat ~/.dot-files/zsh/default-config

source "$(dirname "$0")/.alias"
source "$(dirname "$0")/.prompt"
source "$(dirname "$0")/.zsh-git-info"
source "$(dirname "$0")/.git-prompt.sh"

This does work, perfectly.

What I'm trying to do

I want to change my shell chsh -s /bin/bash, restart terminal. And I expect it to just work.

I have ~/.bashrc I want to point it towards a repo that anyone can clone wherever they want.

I want that repo to reference relative path to where the default-config is. I want to NEVER have a hardcoded full path.

For zsh, source "$(dirname "$0") just works. The steps as I understand them:

• ~/.zshrc calls source on a file directly: ~/.dot-files/zsh/default-config
• said file calls source command, yes, but it inserts "path to me" with $(dirname "$0") followed by the name of a file in the same folder as "me".
  • source "$(dirname "$0")/.alias" transforms to source ~/.dot-files/zsh/.alias

Bash does not work, no idea why.

Answer 1

In Bourne/POSIX shells, the special parameter $0 is set to the name of the script that the shell executes (or the name of the shell itself). It does not change when reading another script file with the . (“dot”) command. Bash follows the standard behavior in this respect, including when using the source synonym of . (“dot”).

In zsh, by default the special parameter $0 is set to the path to the current script or the name of the current function, i.e. it changes when using the . or source builtin, when calling a function, and when returning from a function or script. You can change zsh to the standard behavior by unsetting the option function_argzero (which is set by default unless zsh is in sh or ksh emulation mode) or setting posix_argzero.

In bash, the path to the current script (affected by . or source) is available under the name $BASH_ARGV0.

---

Incidentally, since you know that you have a path to a non-directory file with a directory component, you can use the simple and slightly faster "${0%/*}" to refer to the directory containing it.¹

¹ It's also more robust than "$(dirname -- "$0")" because it works if the directory name ends with a newline, and than "$(dirname "$0")" because it works if the path starts with a dash, but neither of those apply here. It's more fragile because it doesn't work if the path ends with a slash or doesn't contain a slash at all, but that doesn't apply here either.

Answer 2

There are two easy ways to fix your problem:

use pushd/popd

Just change current folder inside the default-config files and restore afterwards:

if pushd ~/.dot-files/bash/ > /dev/null; then
  source ./.alias
  source ./.prompt
  source ./.zsh-git-info
  source ./.git-prompt.sh
  popd > /dev/null
fi

(in zsh, you can use -q instead of redirecting stdout to /dev/null to avoid the dump of the directory stack, but not in bash).

Of course, your default-config files would differ in this one line.

use variable

Define a variable inside .bashrc and .zshrc. The variable will point to where your sourced files are:

# .bashrc
fdir=~/.dot-files/bash
source "${fdir}/default-config"

Do the same for .zshrc

And inside the default-config can be the same for both shells, just reuse this variable:

source "${fdir}/.alias"
source "${fdir}/.prompt"
source "${fdir}/.zsh-git-info"
source "${fdir}/.git-prompt.sh"