Scsh (a ''Scheme shell'') is computer
software, a type of
shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard o ...
for an
operating system. It is a Portable Operating System Interface (
POSIX)
application programming interface
An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how t ...
(API) layered on the programming language
Scheme A scheme is a systematic plan for the implementation of a certain idea.
Scheme or schemer may refer to:
Arts and entertainment
* ''The Scheme'' (TV series), a BBC Scotland documentary series
* The Scheme (band), an English pop band
* ''The Schem ...
, in a manner to make the most of Scheme's ability for
scripting. Scsh is limited to
32-bit
In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculati ...
platforms but there is a development version against the latest
Scheme 48 that works in
64-bit
In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide. Also, 64-bit CPUs and ALUs are those that are based on processor registers, address buses, or data buses of that size. A comput ...
mode. It is
free and open-source software released under the
BSD-3-Clause license.
Features
Scsh includes these notable features:
*
Library support for list, character, and
string manipulations;
*
Regular expressions manipulation support using ''scheme regular expressions'', a
domain-specific language
A domain-specific language (DSL) is a computer language specialized to a particular application domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains. There are a wide variety of DSLs, ranging f ...
(DSL), or little languages, approach to the abilities;
* Strong networking support;
* High-level support for
awk
AWK (''awk'') is a domain-specific language designed for text processing and typically used as a data extraction and reporting tool. Like sed and grep, it is a filter, and is a standard feature of most Unix-like operating systems.
The AWK lan ...
like scripts, integrated into the language as
macros;
* Abstractions supporting
pseudo terminal
In some operating systems, including Unix and Linux, a pseudoterminal, pseudotty, or PTY is a pair of pseudo-device endpoints (files) which establish asynchronous, bidirectional communication ( IPC) channel (with two ports) between two or mor ...
s;
* A
shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard o ...
language, modeled using
quasi-quotation
Quasi-quotation or Quine quotation is a linguistic device in formal languages that facilitates rigorous and terse formulation of general rules about linguistic expressions while properly observing the use–mention distinction. It was introduced ...
.
Example
* Print a list of all the executables available in the current
PATH
A path is a route for physical travel – see Trail.
Path or PATH may also refer to:
Physical paths of different types
* Bicycle path
* Bridle path, used by people on horseback
* Course (navigation), the intended path of a vehicle
* Desire p ...
to the
standard output
In computer programming, standard streams are interconnected input and output communication channels between a computer program and its environment when it begins execution. The three input/output (I/O) connections are called standard input (stdi ...
:
#!/usr/local/bin/scsh -s
!#
(define (executables dir)
(with-cwd dir
(filter file-executable? (directory-files dir #t))))
(define (writeln x) (display x) (newline))
(for-each writeln
(append-map executables ((infix-splitter ":") (getenv "PATH"))))
"Acknowledgments"
The reference manual for Scsh includes a spoof
Acknowledgments section
written by Olin Shivers. It starts:
:''Who should I thank? My so-called "colleagues", who laugh at me behind my back, all the while becoming famous on my work? My worthless graduate students, whose computer skills appear to be limited to downloading bitmaps off of netnews? My parents, who are still waiting for me to quit "fooling around with computers," go to med school, and become a radiologist? My department chairman, a manager who gives one new insight into and sympathy for disgruntled postal workers?''
and concludes with:
:''Oh, yes, the acknowledgements. I think not. I did it. I did it all, by myself.''
See also
*
Unix shell
*
Comparison of command shells
A command shell is a command-line interface to interact with and manipulate a computer's operating system.
General characteristics
Interactive features
Background execution
Background execution allows a shell to run a command without u ...
References
External links
*
*
Sourceforge project page
Unix shells
Scheme (programming language) interpreters
Scheme (programming language) implementations
Scripting languages
Software using the BSD license
{{Unix-stub