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Z Shell: Difference between revisions
Ad a little explanation about what makes Z Shell more and different from Unix Shell
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[http://www.zsh.org/ Zsh Home] | [[wp:z shell|Wikipedia: Z Shell]] | [http://reddit.com/r/zsh Reddit: Zsh]
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 from [[UNIX 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.
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