Unix Shell - यह एक Command Line Interpreter है |
- यह user को Command Line Interface (CLI) प्रदान करता है | जिसकी सहायता से उपयोगकर्ता commands insert कर सकता है |
शैल यूजर द्वारा दिए गए कमांड को इन्टरप्रेट कर सम्पादित करने के लिए कर्नेल (kernel) को भेजता है | कर्नेल उस कमांड को सम्पादित करने के लिए हार्डवेयर को निर्देशित करता है |
- यह एक command language और script language दोनों है |
- यूजर टर्मिनल प्रोग्राम (terminal program) द्वारा shell साथ interact करता है | और इस प्रकार वह UNIX system के साथ interact करता है |
Script - Shell commands को एक साथ जोड़कर हम small program लिख सकते है जिसे Shell Script कहा जाता है |
सभी Unix shells द्वारा filename wildcarding, piping, here documents, command substitution, variables and
control structures (condition-testing and iteration) का support प्रदान किया जाता है |
Shell एक प्रकार का प्रोग्राम है जिसमें user commands type कर सकता है | यह command shell द्वारा kernel को भेजा जाता है |
UNIX like operating systems में कई प्रकार के shell program उपलब्ध है, User की आवश्यकता अनुसार इसे change किया जा सकता है | प्रत्येक user की profile /etc/passwd file में store रहती है |
| Shell Command | Shell Full name | About |
|---|---|---|
| sh | Thompson Shell | First Shell Developed by Ken Thompson at Bell Labs It was available with UNIX 1 to UNIX 6 during 1971 to 1975. Control Structures if and goto. /bin/sh |
| sh | Bourne Shell | Developed by Stephen Bourne at Bell Labs. Distributed with UNIX 7 in 1979. here documents, command substitution, generic variables, control structures, reversed keyword to mark end of block. Path - /bin/sh |
| bash | Bourne Again Shell | Written as part of GNU project. This is default interactive shell on most of the Linux distribution and macOS system. /bin/bash |
| ash | Almquist Shell | BSD licensed replacement of Bourne Shell /bin/ash |
| dash | Debian Almquist Shell | modern replacement for ash in Debian and Ubuntu |
| ksh | Korn Shell | Written by David Korn and based on Bourne Shell at Bell Labs. /bin/ksh |
| pdksh | Public Domain Korn Shell | |
| zsh | Z Shell | modern shell, backward compatible with bash shell, default shell in macOS since 10.15 Catalina |
| csh | C Shell | modeled on C Programming, developed by Bill Joy as graduate student at University of California at Berkeley. Distributed with BSD unix. /bin/csh |
| tcsh | TC shell | /bin/tcsh |
Terminal Emulator - यह एक प्रोग्राम है जो जिसकी सहायता से यूजर शैल को text based command जारी करता है |
उदहारण - GNOME Terminal (GNOME) , xterm (X Window System) , Konsole, Guake, Terminator, Tilda, PuTTY (SSH and Telnet), ROXTerm, Eterm, rxvt (extended virtual terminal),
~/.bashrc - shell script which is run whenever a shell / terminal is started. It is located in the user's home directory. It initializes interactive shell session.
GNU - GNU's Not Unix, It is an operating system. It is pronounced as g'noo.
BSD - Berkeley Software Distribution, an Operating System, developed at University of California, Berkeley.
GNOME - free and open-source desktop environment for UNIX like operating systems. Current version is GNOME 3. Website : https://www.gnome.org/gnome-3/
KDE - International Free Software Community, develops free software. K(ool) Desktop Environment