Re: Which shell and how to get started handling arguments

On 2024-04-16, Kenny McCormack <gazelle@shell.xmission.com> wrote:

ISTR (which is to say, I can't prove it or point to an example at the
moment), that there were some systems under some circumstances where if
bash was copied/linked as "sh" (and then run as "sh" instead of "bash"),
then it did indeed behave like a plain "POSIX" shell (i.e., extensions were
disabled).

From the man page:
  If bash is invoked with the name sh, it tries to mimic the startup
  behavior of historical versions of sh as closely as possible, while
  conforming to the POSIX standard as well. [...]
  When invoked as sh, bash enters posix mode after the startup files are
  read.

However, it is possible to disable a lot of features at build time.
In particular, configuring bash with --enable-minimal-config produces
a much reduced feature set:

dnl a minimal configuration turns everything off, but features can be
dnl added individually
if test $opt_minimal_config = yes; then
        opt_job_control=no opt_alias=no opt_readline=no
        opt_history=no opt_bang_history=no opt_dirstack=no
        opt_restricted=no opt_process_subst=no opt_prompt_decoding=no
        opt_select=no opt_help=no opt_array_variables=no opt_dparen_arith=no
        opt_brace_expansion=no opt_disabled_builtins=no opt_command_timing=no
        opt_extended_glob=no opt_cond_command=no opt_arith_for_command=no
        opt_net_redirs=no opt_progcomp=no opt_separate_help=no
        opt_multibyte=yes opt_cond_regexp=no opt_coproc=no
        opt_casemod_attrs=no opt_casemod_expansions=no opt_extglob_default=no
        opt_translatable_strings=no
        opt_globascii_default=yes
fi

--
Christian "naddy" Weisgerber                          naddy@mips.inka.de