Error: couldn't detect shell type. Please specify your…

Error message

Error: couldn't detect shell type. Please specify your shell with `%s`

What it means

`hub alias` prints a shell snippet that aliases `git` to `hub`. It detects the current shell from $SHELL (or $ZSH_VERSION/$BASH_VERSION style hints); if detection yields an empty string, it calls utils.Check with this error, telling you to pass the shell explicitly. utils.Check prints the message and exits, so this is fatal.

Solutions

Pass the shell explicitly: `hub alias bash` or `hub alias -s zsh` as the error message suggests.
Export SHELL in the environment: export SHELL=$(basename $SHELL) before running hub alias.
If using an unsupported shell, write the alias manually using the closest supported output (bash/zsh/fish) as a template.

Example fix

// before
eval "$(hub alias -s)"   # fails when SHELL is empty
// after
eval "$(hub alias -s zsh)"

Defensive patterns

Strategy: validation

Validate before calling

if [ -z "$SHELL" ]; then
  eval "$(hub alias -s bash)"   # pass shell explicitly when SHELL is unset
else
  eval "$(hub alias -s "$(basename "$SHELL")")"
fi

Prevention

Always pass the shell explicitly in scripts: hub alias -s zsh.
Ensure SHELL is exported in non-interactive environments.
Pin the alias generation to a known shell in dotfiles installers.

When it happens

Trigger: Running `hub alias` (or `hub alias -s`) non-interactively — e.g. in scripts, cron, CI, or eval "$(hub alias -s)" contexts — where $SHELL is unset/empty so no shell type can be inferred.

Common situations: Sourcing the alias snippet from a script where SHELL isn't exported; running under shells hub can't infer (nushell, elvish, xonsh); cron jobs lacking the interactive env; Windows environments without SHELL.

Related errors

AI-assisted analysis of mislav/hub@5c547ed804 (2026-09-01). Data as JSON: /api/errors/7c2bccf168285055. Report an issue: GitHub.

Appendix: source

Thrown at commands/alias.go:50

func init() {
	CmdRunner.Use(cmdAlias)
}

func alias(command *Command, args *Args) {
	var shell string
	if args.ParamsSize() > 0 {
		shell = args.FirstParam()
	} else {
		shell = os.Getenv("SHELL")
	}

	flagAliasScript := args.Flag.Bool("-s")
	if shell == "" {
		cmd := "hub alias <shell>"
		if flagAliasScript {
			cmd = "hub alias -s <shell>"
		}
		utils.Check(fmt.Errorf("Error: couldn't detect shell type. Please specify your shell with `%s`", cmd))
	}

	shells := []string{"bash", "zsh", "sh", "ksh", "csh", "tcsh", "fish", "rc"}
	shell = filepath.Base(shell)
	var validShell bool
	for _, s := range shells {
		if s == shell {
			validShell = true
			break
		}
	}

	if !validShell {
		err := fmt.Errorf("hub alias: unsupported shell\nsupported shells: %s", strings.Join(shells, " "))
		utils.Check(err)
	}

	if flagAliasScript {

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