1 / 9

Linux Shells

Linux Shells. Dr. Michael L. Collard www.sdml.info/collard www.sdml.info/collard/linux collard@cs.kent.edu. Command Line Interface. Start application programs File handling System administration Basically, layer over kernel API Scripting language

wing-richards
Télécharger la présentation

Linux Shells

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Linux Shells Dr. Michael L. Collard www.sdml.info/collard www.sdml.info/collard/linux collard@cs.kent.edu

  2. Command Line Interface • Start application programs • File handling • System administration • Basically, layer over kernel API • Scripting language • Internal (built-in to shell) and external commands (separate programs)

  3. Thomson shell (sh) • Ken Thomson, 1971 • First Unix shell in the first release of Unix • Simple command interpreter • Not really a scripting language

  4. Bourne shell (sh) • Stephen Bourne, ATT&T Bell Labs (1977) • /bin/sh - Replacement for Thomson shell • Released in 1977 as the default Unix shell of Unix Version 7 • Default shell for the root (superuser) account • Descendants: ksh, rc, bash, dash

  5. C Shell (csh) • Bill Joy for BSD, 1978 • Derived from Thomson shell (original sh) • Syntax modeled after C • Good job control features, history • tcsh – C shell (csh) with features, e.g., command-line editing • Typical usage: • C Shell (csh) for interactive use (or tcsh) • Bourne shell (sh) for scripting

  6. Korn shell (ksh) • David Korn, 1988 (ksh88) • Syntax of Bourne shell (sh) and features of C Shell (csh) • Basis for POSIX shell • Ksh93 • Variants: dtksh (part of CDE), tksh (with Tk)

  7. Bash Shell (bash) • “Bourne-Again” shell • GNU Project, 1987 • Superset of Bourne shell (sh) • Features of C Shell (csh), and tcsh • Default for most modern Linux distributions, Mac OS X, Cygwin • “bashisms” – features/behavior not in Bourne shell (sh)

  8. Other Shells • rc – replacement for sh on Plan 9 • ash, Almquist shell, A Shell – clone for BSD of much of Bourne shell • dash – Debian Almquist shell, faster then bash, but no extensions (no “bashisms”) • esh – Easy Shell, Lisp based • scsh – Scheme shell • sash – Standalone shell, no reliance on external libraries • zsh – Z Shell extension of Bourne shell

  9. Current Practice • /bin/sh – Bourne shell, default for root account • /bin/bash – Bourne-Again shell, default for users • Typically, /bin/sh alias for /bin/bash, but may not support same features • /etc/shells – list of installed shells • Other shells provided for compatibility with existing scripts

More Related