shebang
(Or "shebang line", "bang path") /sh*-bang'/ (From "sharp" and "bang") The magic cookie "#!" used in Unix to mark the start of a script, e.g. a shell script or Perl script.
Under Unix, if the first two bytes of an executable file are "#!", the kernel treats the file as a script rather than a machine code program. The word following the "!" (i.e., everything up to the first whitespace) is used as the pathname of the interpreter. For example, if the first line of an executable is#!/usr/local/bin/perlthe script will be treated as a Perl script and passed as an argument to /usr/local/bin/perl to be interpreted. Some variants of Unix also allow one or more parameters to be passed to the interpreter, for example, you can write
#!/usr/bin/perl -wand the script will be started as if you typed
/usr/bin/perl -w <filename>on the command line. Also, most modern kernels ignore any whitespace between the "!" and the interpreter pathname. Even some modern kernels have fairly small limits (e.g. 32) on the length of line they will accept, making long pathnames and arguments somewhat unportable. [Does anyone call this a "magic string"?]
Last updated: 1998-05-06
SHEEP
<mathematics, tool>
A package for symbolic mathematics, especially tensor analysis and General Relativity, developed by Inge Frick in Stockholm in the late 1970s to early 1980s. SHEEP was implemented in DEC-10 assembly language, then in several LISPs. The current version runs on Sun-3 and is based on Portable Standard LISP.
["Sheep, a Computer Algebra System for General Relativity", J.E.F. Skea et al in Proc First Brazilian School on Comp Alg, W. Roque et al eds, Oxford U Press 1993, v2]. http://riaca.win.tue.nl/archive/can/SystemsOverview/Special/Tensoranalysis/SHEEP/index.html.Last updated: 2002-12-28
shelf
A public library of classes for the Eiffel language.shelfware
<jargon>
/shelfweir/ Software which is never used and so ends up on the shelf. Shelfware may be purchased on a whim by an individual, or in accordance with corporate policy, but not actually required for any particular use. Alternatively, it may be software that has been developed (unlike vaporware), but is never released as a product -- a common occurrence at DEC.
[Jargon File]Last updated: 1997-07-20
SHELL
<language>
An early system on the Datatron 200 series.
[Listed in CACM 2(5):16 (May 1959)]. [Jargon File]Last updated: 1995-05-11
shell
1. (Originally from Multics, widely propagated via Unix) The command interpreter used to pass commands to an operating system; so called because it is the part of the operating system that interfaces with the outside world.
The commonest Unix shells are the c shell (csh) and the Bourne shell (sh). 2. (Or "wrapper") Any interface program that mediates access to a special resource or server for convenience, efficiency, or security reasons; for this meaning, the usage is usually "a shell around" whatever. [Jargon File]Last updated: 1995-05-11
shell out
[Unix] To spawn an interactive subshell from within a program (e.g. a mailer or editor). "Bang foo runs foo in a subshell, while bang alone shells out." [Jargon File]Last updated: 1995-05-11
shell script
<programming, operating system>
A program written to be interpreted by the shell of an operating system, especially Unix.
Compare: script, glue language.Last updated: 1999-02-22
shell variable
<programming, operating system>
One of the variables accessible to a Unix shell process, including environment variables (e.g. $HOME), command line arguments (e.g. $1) and local variables (e.g. $input_file). Other operating systems have similar variables.
Last updated: 1999-01-26
Nearby terms:
shar file ♦ sharp ♦ Sharp APL ♦ S-HDSL ♦ shebang ♦ SHEEP ♦ shelf ♦ shelfware ♦ SHELL
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