zsh

migration from bash

The manual is a number of sections:

Command interpreter (shell) zsh is usable as an interactive login shell and as a shell script command processor. Of the common shells, zsh resembles ksh with many enhancements. It does not provide compatibility with POSIX or other shells by default.

Includes command line editing, spelling correction, programmable command completion, shell functions (with autoloading), a history mechanism.

To set the default shel use chsh -s /bin/bash

Without -c or -s remaining arguments, after option processing, the first argument is a script

• With PATH_SCRIPT , and the name does not contain a directory path (i.e. there is no `/' in the name), first the current directory then the command path given by $PATH are searched.
  
• Without PATH_SCRIPT or the file name contains a `/' it is used directly.

After the first one or two arguments , the remaining arguments are assigned to the positional parameters.

see zshoptions.

Options

 zsh -o shwordsplit scr 

$ setopt extended_glob
$ echo hello # hello : hello  --- a history pattern match
zsh: bad pattern: #

$ unsetopt extended_glob
$ echo hello # hello : hello --- a regular character
hello # hello : hello

$ setopt interactive_comments
$ echo hello # hello : hello    --- a comment for the rest of the line.
hello

$ histchars[3]=:                --- changing  to use : as comment leading.
$ echo hello # hello : hello
hello # hello

bash interactive_comments  on by default in interactive shells.

$ echo hello # hello
hello
$ shopt -u interactive_comments   unset it
$ echo hello # hello
hello # hello

if [ -e .vimrc    bash true if .vimrc exists, zsh ...
if [ -a .vimrc    bash true if .vimrc exists, zsh [: too many arguments
if [ -d /Volume/DATA    bash true if /Volume/DATA exists, zsh false




$x == 0   #  expected logical test to return result
zsh: = not found

$x=';'   # expected x to be assigned string value of ;
zsh: ; not found

$x="x"  # expected x to be assigned string value of  x
     .zprofile is executed !

When encounters:
set   editing-mode vi 
zsh reports  zsh:1: command not found: editing-mode


set |g vi
'*'=( editing-mode vi )
@=( editing-mode vi )
argv=( editing-mode vi )

set

'!'=0           also  echo $! reports  0
'#'=2
'$'=5982
'*'=( editing-mode vi )
-=569Xils
0=-zsh
'?'=127
@=( editing-mode vi )

$SHELL=/bin/zsh
SHELL_SESSION_DID_HISTORY_CHECK=1
SHELL_SESSION_DID_INIT=1
SHELL_SESSION_HISTORY=1
SHELL_SESSION_DIR=/Users/$USER/.zsh_sessions
SHELL_SESSION_FILE=/Users/$USER/.zsh_sessions/C75FC5F8-92F5-4886-92D7-F2FB6FC7516D.session
                                    1/14/22 227 files since Dec 28, increasing in size fo 40KB to 100kb !
SHELL_SESSION_HISTFILE=/Users/$USER/.zsh_sessions/C75FC5F8-92F5-4886-92D7-F2FB6FC7516D.history
SHELL_SESSION_HISTFILE_NEW=/Users/$USER/.zsh_sessions/C75FC5F8-92F5-4886-92D7-F2FB6FC7516D.historynew    0 created at login(?)
SHELL_SESSION_HISTFILE_SHARED=/Users/$USER/.zsh_history
SHELL_SESSION_TIMESTAMP_FILE=/Users/$USER/.zsh_sessions/_expiration_check_timestamp
ZSH_SUBSHELL=1

When is compared with the emulate command : variables that conflict with POSIX usage such as path are not defined.

In sh and ksh compatibility modes :

• ARGC, argv, cdpath, fignore, fpath, HISTCHARS, mailpath, MANPATH, manpath, path, prompt, PROMPT, PROMPT2, PROMPT3, PROMPT4, psvar, status and watch are not special and not initialized.
  
• The zsh startup/shutdown scripts are not executed.
• Profile scripts are /etc/profile, $HOME/.profile.
• If $ENV is set on invocation, it is sourced after the profile scripts. The value of ENV is subjected to parameter expansion, command substitution, and arithmetic expansion before being interpreted as a pathname. PRIVILEGED affects the execution of startup files.
• NO_BAD_PATTERN, NO_BANG_HIST, NO_BG_NICE, NO_EQUALS, NO_FUNCTION_ARGZERO, GLOB_SUBST, NO_GLOBAL_EXPORT, NO_HUP, INTERACTIVE_COMMENTS, KSH_ARRAYS, NO_MULTIOS, NO_NOMATCH, NO_NOTIFY, POSIX_BUILTINS, NO_PROMPT_PERCENT, RM_STAR_SILENT, SH_FILE_EXPANSION, SH_GLOB, SH_OPTION_LETTERS, SH_WORD_SPLIT are set.

Invoked as ksh KSH_OPTION_PRINT, LOCAL_OPTIONS, PROMPT_BANG, PROMPT_SUBST and SINGLE_LINE_ZLE are set.

builtin commands NOT in bash

autoload [ {+|-}UXktz ] [ -w ] [ name … ]

Equivalent to functions -u, with the exception of -X/+X and -w.
-X may be used only inside a shell function, and may not be followed by a name, causes the calling function to be marked for autoloading and then immediately loaded and executed, with the current array of positional parameters as arguments. This replaces the previous definition of the function.
If no function definition is found, an error is printed and the function remains undefined and marked for autoloading.
+X loads each name as an autoloaded function, but does not execute it.
The exit status is zero (success) if the function was not previously defined and a definition for it was found.
This does not replace any existing definition of the function.
The exit status is nonzero (failure) if the function was already defined or when no definition was found. In the latter case the function remains undefined and marked for autoloading.
If ksh-style autoloading is enabled, the function created will contain the contents of the file plus a call to the function itself appended to it, giving normal ksh autoloading behaviour on the first call to the function.

With -w files are compiled with zcompile builtin and functions defined in them are marked for autoloading.

-z and -k mark the function to be autoloaded in native or ksh emulation, as if KSH_AUTOLOAD were unset or were set, respectively. The flags override the setting of the option at the time the function is loaded.

STARTUP/SHUTDOWN FILES

If $ZDOTDIR is unset $HOME is used .

At startup

1. /etc/zshenv Commands are read, this cannot be overridden.
   Apple mac os, none is present

   Run for all instances of zsh and should be as small as possible. Code that does not need to be run for every shell should be behind a test of the form if [[ -o rcs ]]; then … so that it will not be executed when zsh is invoked with -f.

   RCS (set by default) if unset supresses processing of subsequent startup files.
   GLOBAL_RCS (set by default) if unset supresses processing of subsequent global startup files (those shown here with an path starting with a /).
   A file in $ZDOTDIR can re-enable GLOBAL_RCS.

2. $ZDOTDIR/.zshenv
3. /etc/zprofile
   Apple mac os has
   • if [ -x /usr/libexec/path_helper ]; then
eval `/usr/libexec/path_helper -s`
4. $ZDOTDIR/.zprofile for a login shell, $ZDOTDIR/.zshrc for interactive.
   Apple mac os for /etc/zshrc has :
   • disable log
   • HISTFILE=${ZDOTDIR:-$HOME}/.zsh_history # Save command history
   • HISTSIZE=2000
   • SAVEHIST=1000
   • setopt BEEP # Beep on error
   • PS1="%n@%m %1~ %# " # prompt uname @ host %
   • PS1="%m %1~ %# " # without uname
   • many key bindings there
   zshrc_Apple_Terminal
   • Tell the terminal about the current working directory at each prompt.
   • big hairy stuff
5. /etc/zlogin
6. $ZDOTDIR/.zlogin for a login shell

When the login shell exits:

1. $ZDOTDIR/.zlogout
2. /etc/zlogout are processed unless the shell terminates due to exec'ing another process

Compiled files newer than the original will be used (see zshbuiltins zcompile).

FILES

       $ZDOTDIR/.zshenv
       $ZDOTDIR/.zprofile
       $ZDOTDIR/.zshrc
       $ZDOTDIR/.zlogin
       $ZDOTDIR/.zlogout
       ${TMPPREFIX}*   (default is /tmp/zsh*)
       /etc/zshenv
       /etc/zprofile
       /etc/zshrc
       /etc/zlogin
       /etc/zlogout    (installation-specific - /etc is the default)

SEE ALSO sh(1), csh(1), tcsh(1), rc(1), bash(1), ksh(1), zshall(1), zshbuiltins(1), zshcompwid(1), zshcompsys(1), zshcompctl(1), zshcontrib(1), zshexpn(1), zshmisc(1), zshmodules(1), zshoptions(1), zshparam(1), zshroadmap(1), zshtcpsys(1), zshzftpsys(1), zshzle(1)

A user guide is at http://zsh.sourceforge.net/Guide/. At