Editing Bourne shell (section)

===Features of the original version===
Features of the Version 7 UNIX Bourne shell include:

* Scripts can be invoked as commands by using their filename
* May be used interactively or non-interactively
* Allows both synchronous and asynchronous execution of commands
* Supports input and output redirection and pipelines
* Provides a set of built-in commands
* Provides flow control constructs and quotation facilities.
* Typeless variables
* Provides local and global variable scope
* Scripts do not require compilation before execution
* Does not have a goto facility, so code restructuring may be necessary
* [[Command substitution]] using [[backquotes]]: <code>`command`</code>.
* [[Here documents]] using <code>&lt;&lt;</code> to embed a block of input text within a script.
* <code>for ~ do ~ done</code> loops, in particular the use of <code>$*</code> to loop over arguments, as well as <code>for ~ in ~ do ~ done</code> loops for iterating over lists.
* <code>case ~ in ~ esac</code> selection mechanism, primarily intended to assist [[argument parsing]].
* <code>sh</code> provided support for environment variables using keyword parameters and exportable variables.
* Contains strong provisions for controlling input and output and in its [[regular expression|expression matching]] facilities.

The Bourne shell also was the first to feature the convention of using [[file descriptor]] <code>2&gt;</code> for [[error message]]s, allowing much greater programmatic control during scripting by keeping error messages separate from data.

Stephen Bourne's coding style was influenced by his experience with the [[ALGOL 68C]] compiler<ref name="reader">{{cite tech report |first1=M. D. |last1=McIlroy |author-link1=Doug McIlroy |year=1987 |url=http://www.cs.dartmouth.edu/~doug/reader.pdf |archive-url=https://web.archive.org/web/20140504225225/http://www.cs.dartmouth.edu/~doug/reader.pdf |archive-date=2014-05-04 |url-status=live |title=A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 |series=CSTR |number=139 |institution=Bell Labs}}</ref> that he had been working on at [[University of Cambridge|Cambridge University]]. In addition to the style in which the program was written, Bourne reused portions of [[ALGOL 68]]'s <code>'''if''' ~ '''then''' ~ '''elif''' ~ '''then''' ~ '''else''' ~ '''fi'''</code>, <code>'''case''' ~ '''in''' ~ '''esac'''</code> and <code>'''for'''/'''while''' ~ '''do''' ~ '''od'''</code>" (using <code>done</code> instead of <code>'''od'''</code>) clauses in the common [[Unix]] Bourne shell syntax. Moreover, – although the v7 shell is written in [[C (programming language)|C]] – Bourne took advantage of some [[Macro (computer science)|macros]]<ref>{{Cite web| url=http://minnie.tuhs.org/cgi-bin/utree.pl?file=V7/usr/src/cmd/sh/mac.h|title=mac.h – Macros used by Bourne to structure C like Algol68C |access-date=9 September 2006|author=Bourne, Steve|author-link=Stephen R. Bourne|date= 12 January 1979 |publisher=[[AT&T Corporation]] }}</ref> to give the C [[source code]] an ALGOL 68 flavor. These macros (along with the [[Finger protocol|finger]] command distributed in Unix version [[Berkeley Software Distribution#4.2BSD|4.2BSD]]) inspired the [[International Obfuscated C Code Contest]] (IOCCC).<ref>{{Cite web|url=http://www.ioccc.org/faq.html|title=The IOCCC FAQ – Q/A: How did the IOCCC get started?| access-date=9 September 2006|author=Landon Curt Noll|author-link=Landon Curt Noll|author2=Simon Cooper|author3=Peter Seebach|author4=Leonid A. Broukhis|name-list-style=amp|year= 2004|publisher=ioccc.org}}</ref>