Shell script

A shell script is a computer program designed to be run by the Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages.

Typical operations performed by shell scripts include file manipulation, program execution, and printing text. A script which sets up the environment, runs the program, and does any necessary cleanup, logging, etc. is called a wrapper.

The term is also used more generally to mean the automated mode of running an operating system shell; in specific operating systems they are called other things such as batch files (MSDos-Win95 stream, OS/2), command procedures (VMS), and shell scripts (Windows NT stream and third-party derivatives like 4NT—article is at cmd.exe), and mainframe operating systems are associated with a number of terms.

The typical Unix/Linux/Posix-compliant installation includes the Korn Shell (ksh) in several possible versions such as ksh88, Korn Shell '93 and others. The oldest shell still in common use is the Bourne shell (sh); Unix systems invariably include also the C Shell (csh), Bourne Again Shell (bash), a remote shell (rsh), a secure shell for SSL telnet connections (ssh), and a shell which is a main component of the Tcl/Tk installation usually called tclsh; wish is a GUI-based Tcl/Tk shell. The C and Tcl shells have syntax quite similar to that of said programming languages, and the Korn shells and Bash are developments of the Bourne shell, which is based on the ALGOL language with elements of a number of others added as well. On the other hand, the various shells plus tools like awk, sed, grep, and BASIC, Lisp, C and so forth contributed to the Perl programming language.

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