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Z Shell is a POSIX-compatible shell, but with much more to offer. Script programs can be written in Z Shell, using modules and advanced variable and pattern handling, that rival compiled languages like C and that no standard POSIX shell could do. Following are some examples:

To replace the system 'sleep' command with a shell function that accepts floating point seconds, minutes, hours, days, or weeks:

function delay sleep {  emulate -LR zsh -o extendedglob -o nullglob  local -F 32 Delay  if [[ $1 == (#b)(digit:(#c1,).(#c0,1)digit:(#c0,))(s|m|h|d|w|) ]]  then    if [[ $match[2] == (s|) ]] Delay=$[ $match[1] ]    if [[ $match[2] == (m) ]] Delay=$[ $match[1] * 60. ** 1 ]    if [[ $match[2] == (h) ]] Delay=$[ $match[1] * 60. ** 2 ]    if [[ $match[2] == (d) ]] Delay=$[ ($match[1] * 60. ** 2) * 24 ]    if [[ $match[2] == (w) ]] Delay=$[ (($match[1] * 60. ** 2) * 24) * 7 ]    : $(read -u 1 -t $Delay)  else    print -u 2 "Invalid delay time: $1"    return 1  fi}

To replace the system's "cat" command for standard input and output:

function zsh_cat {  emulate -LR zsh  zmodload zsh/system  local buffer  while sysread buffer  do    syswrite $buffer  done}

The zsh_cat function, in particular, is a good, basic example of what cannot be done in the popular bash/sh. Z Shell can do much more. Here are just a few more of Z Shell capabilities:

• Open TCP ports on file-descriptors
• Copy/move files with Zsh builtins
• Do FTP transactions
• Match filename patterns and string patterns with the Zsh-super-advanced glob-pattern matching, Regex, or PCRE regex.
• Emulate other shells with great precision, making Zsh the only shell needed on a typical system:
  • SH/Bash
  • Csh
  • Ksh
• Load and run pre-parsed/compiled word-code files, speeding up the execution of scripts and autoload functions. Also, this makes possible distributing a collection of pre-compiled autoload functions all as one .zwc file that can be likened to a plugin or an app that will run on any Zsh system (like a .Net exe or a Java jar).
• Load new modules made for the current version of Zsh, like a native graphical front-end for "Zsh apps". (For graphical, it is probably better to just use an input-output interface to wish, the Tcl/Tk GUI)

With all Zsh can do, it is worthy of being considered a language of its own, separate fromUNIX Shell but fully compatible. Though the executable for Zsh is much smaller than Bash, much of the extra capabilities, including Regex matching and new-user-detection load from modules and function autoload files. These numerous other files can be customized extensively, potentially creating system command/invocation incompatibilities. These can be overcome by using the standard option "-f", and by using the either the correct command name ("/bin/"(zsh|sh|ksh|bash)) or an emulation command ("emulate <shell> <shell-options>"). These features can ensure that the code written will be interpreted exactly how it is intended to be.

• Implementations
• UNIX Shell Implementations
• UNIX Shell related