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The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same name, sh. It was developed by Stephen Bourne, of AT&T Bell Laboratories, and was released in 1977 in the Version 7 Unix release distributed to colleges and universities. It remains a popular default shell for Unix accounts. The binary program of the Bourne shell or a compatible program is located at
The shell was designed as a replacement for the original Thompson shell.
Among the primary goals were:
In March 2009 Computerworld published an in-depth interview with Steve Bourne The A-Z of Programming Languages: Bourne shell, or sh which details the Bourne Shell origins and design decisions.
Features of the Bourne shell include:
Although it is used as an interactive command interpreter, it was always intended as a scripting language. It gained popularity with the publication of The UNIX Programming Environment by Brian W. Kernighan and Rob Pike. This was the first commercially published book that presented the shell as a programming language in a tutorial form.
The Bourne shell also was the first to feature the convention of using file descriptor
Over the years, the Bourne shell was enhanced at AT&T. The various variants are thus called like the respective AT&T Unix version it was released with (some important variants being Version7, SystemIII, SVR2, SVR3, SVR4). As the shell was never versioned, the only way to identify it was testing its features.
Stephen Bourne carried into this shell some aspects of the ALGOL 68C compiler that he had been working on at Cambridge University. Notably he reused portions of ALGOL 68's "
The Korn shell (ksh) written by David Korn, was a middle road between the Bourne shell and the C shell. Its syntax was chiefly drawn from the Bourne shell, while its job control features resembled those of the C shell. The functionality of the original Korn Shell (known as ksh88 from the year of its introduction) was used as a basis for the POSIX shell standard. A newer version, ksh93, has been open source since 2000 and is used on some Linux distributions. There is also a clone of ksh88 known as pdksh, and this is the default shell for all users of OpenBSD.
Due to copyright issues surrounding the Bourne Shell as it was used in historic CSRG BSD releases, Kenneth Almquist developed a clone of the Bourne Shell, known by some as the Almquist Shell and available under the BSD license, which is in use today on some BSD descendants and in low-memory situations. The Almquist Shell was ported to Linux, and the port renamed the Debian Almquist shell, or dash. This shell provides much faster execution of standard sh scripts with a smaller memory footprint than its more common counterpart, bash. Its use tends to expose bashisms - bash-centric assumptions made in scripts meant to run on sh.
The Bourne shell was once standard on all branded Unix systems, although historically BSD-based systems had many scripts written in csh. Bourne shell scripts can typically be run with bash or dash on GNU/Linux or other Unix-like systems.
"Nobody really knows what the Bourne shell's grammar is. Even examination of the source code is little help."