texinode(Compatibility)(Prompt Expansion)(Conditional Expressions)(Top)
chapter(Compatibility)
ifzman(\
sect(Compatibility)
)\
cindex(compatibility)
cindex(sh, compatibility)
cindex(ksh, compatibility)
Zsh tries to emulate bf(sh) or bf(ksh) when it is invoked as
tt(sh) or tt(ksh) respectively.  In this mode the following
parameters are not special and not initialized by the shell:
tt(ARGC),
tt(argv),
tt(cdpath),
tt(fignore),
tt(fpath),
tt(HISTCHARS),
tt(mailpath),
tt(MANPATH),
tt(manpath),
tt(path),
tt(prompt),
tt(PROMPT),
tt(PROMPT2),
tt(PROMPT3),
tt(PROMPT4),
tt(psvar),
tt(status),
tt(watch).

The usual zsh startup/shutdown scripts are not executed.  Login shells
source tt(/etc/profile) followed by tt($HOME/.profile).  If the
tt(ENV) environment variable is set on invocation, tt($ENV) is sourced
after the profile scripts.  The value of tt(ENV) is subjected to
parameter expansion, command substitution, and arithmetic expansion before
being interpreted as a pathname.  Note that the tt(PRIVILEGED) option
also affects the execution of startup files.

The following options are set if the shell is invoked as tt(sh) or
tt(ksh):
tt(NO_BAD_PATTERN),
tt(NO_BANG_HIST),
tt(NO_BG_NICE),
tt(NO_EQUALS),
tt(NO_FUNCTION_ARGZERO),
tt(GLOB_SUBST),
tt(NO_HUP),
tt(INTERACTIVE_COMMENTS),
tt(KSH_ARRAYS),
tt(NO_MULTIOS),
tt(NO_NOMATCH),
tt(NO_NOTIFY),
tt(POSIX_BUILTINS),
tt(NO_PROMPT_PERCENT),
tt(RM_STAR_SILENT),
tt(SH_FILE_EXPANSION),
tt(SH_GLOB),
tt(SH_OPTION_LETTERS),
tt(SH_WORD_SPLIT).
Additionally the tt(BSD_ECHO) and tt(IGNORE_BRACES)
options are set if zsh is invoked as tt(sh).
Also, the
tt(KSH_OPTION_PRINT),
tt(LOCAL_OPTIONS),
tt(PROMPT_BANG),
tt(PROMPT_SUBST)
and
tt(SINGLE_LINE_ZLE)
options are set if zsh is invoked as tt(ksh).