Saturday 29 September 2012

LINUX shells

DEFINITION

  • Shell is an command language interpreter that executes commands read from the standard input device ( keyboard ) or from a file.
  • Shell is a user program or it's environment provided for user interaction.
  • The shell accepts a user’s entries, interprets them, converts them to system calls, and delivers system messages back to the user.


VARIOUS LINUX SHELL
  1. Bash shell (sh command)
  2. C shell (csh command)
  3. korn shell (ksh command)
  4. tcsh shell
  5. ash shell


Bash shell ( sh )

  • Default shell for most Linux distro.
  • Acronym for Bourne aagain Shell.
  • Includes features originally developed for sh and ksh shells in early UNIX systems , as well as some csh features.

C Shell ( csh )

  • csh shell was created by Bill Joy and used with most Berkeley UNIX systems (such as those produced by Sun Microsystems) as the default shell.
  • Its syntax is modeled after the C programming language.
  • While you can run both csh and tcsh on most Linux systems, both commands actually point to the same executable file. 

Korn shell ( ksh )

  • created by David Korn at AT&T Bell Labs and is the successor to the sh shell.
  • Offers rich scripting capabilities.
  • became the default and most commonly used shell with UNIX System V systems.

tcsh shell


  • open source version of the C shell (csh).
  • Enhanced C shell with file name completion and command line editing.

ash shell

  • lightweight version of the Berkeley UNIX sh shell.
  • It doesn’t include many of the sh shell’s basic features, and is missing such features as command histories. Kenneth Almquist created the ash shell.
  • good shell for embedded systems that have fewer system resources available.





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