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Sam (text editor)
Encyclopedia
Sam is a multi-file text editor
based on structural regular expressions. It was originally designed in the early 1980s at Bell Labs
by Rob Pike with the help of Ken Thompson and other Unix developers for the Blit
windowing terminal running on Unix
; it was later ported to other systems. Sam follows a classical modular
Unix
aesthetic. It is internally simple, its power leveraged by the composability of a small command language and extensibility
through shell integration.
and may be used to operate the editor from a standard text terminal. By default, however, Sam presents its own Graphical User Interface
window, "samterm," which additionally allows point-and-click operations through Smalltalk
-80-style pop-up context menus. This two-process structure allowed sam to access files on networked host systems through remote execution of the file-access process while running the windowing interface locally, thereby bypassing latency over slow connections in its GUI
.
Samterm presents windows to files being edited and to at least one persistent command window which accepts input as sam commands. Most common editing operations are quickly and naturally accomplished with the point-and-click interface, which also functions inside the command window. This latter fact allows commands to be edited (and resubmitted) just as any other text, a function inherited from the DMD 5620 terminal interface.
Sam's command syntax is formally similar to ed
's or ex
's, containing (structural-) regular-expression-based conditional and loop functions and scope addressing, even sharing some of ed's syntax for such functions. But while ed's commands are line-oriented, sam's are selection-oriented. Selections are contiguous strings of text (which may span multiple lines), and are specified either with the mouse (by "sweeping" it over a region of text) or by a pattern match
. Sam's commands take such selections as basic—more or less as other Unix tools treat lines; thus, multi-line and sub-line patterns are as naturally handled by Sam as whole-line patterns are by ed, vi
, awk, Perl, etc. This is implemented through a model called "structural regular expressions," which can recursively apply regular-expression matching to obtain other (sub)selections within a given selection. In this way, sam's command set can be applied to substrings that are identified by arbitrarily complex context.
Sam extends its basic text-editing command set to handling of multiple files, providing similar pattern-based conditional and loop commands for filename specification. Any sequence of text-editing commands may be applied as a unit to each such specification.
Sam was one of the first text editors to support "infinite" undo
to revert any number of editing errors. This feature, combined with Sam's facility to easily edit its own commands and, fundamentally, its small, orthogonal command set (containing only 33 commands), represent the program's bias toward a low learning threshold over other more expressive "power editors."
Sam is the preferred text editor of many eminent computer scientists; it replaced ed as Ken Thompson's favorite text editor, and he still uses it to this day. Sam is the text editor used by Bjarne Stroustrup
and Brian Kernighan
. Others, like Dennis Ritchie
, had moved on to use acme
instead.
Sam vs. acme editor wars occur in the Plan 9
community (both are shipped with Plan 9) although both stem from a similar aesthetic bias. (In fact, both were written by Rob Pike.)
The latest incarnation of sam was written as part of the Plan 9 operating system, but there are Microsoft Windows
and X Window System
ports available.
Text editor
A text editor is a type of program used for editing plain text files.Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code....
based on structural regular expressions. It was originally designed in the early 1980s at Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
by Rob Pike with the help of Ken Thompson and other Unix developers for the Blit
Blit (computer terminal)
In computing, the Blit was a programmable bitmap graphics terminal designed by Rob Pike and Bart Locanthi Jr. of Bell Labs in 1982.When initially switched on, the Blit looked like an ordinary textual terminal, although taller than usual: Similar to the VT100 it had an addressable cursor and...
windowing terminal running on Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
; it was later ported to other systems. Sam follows a classical modular
Modularity (programming)
Modular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...
Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
aesthetic. It is internally simple, its power leveraged by the composability of a small command language and extensibility
Extensibility
In software engineering, extensibility is a system design principle where the implementation takes into consideration future growth. It is a systemic measure of the ability to extend a system and the level of effort required to implement the extension...
through shell integration.
Design and features
Sam is designed as two synchronous programs: a command interpreter and a mouse-oriented bitmap windowing interface. The interpreter's command set is modeled after the UNIX editor edEd (text editor)
ed is a line editor for the Unix operating system. It was one of the first end-user programs hosted on the system and has been standard in Unix-based systems ever since. ed was originally written in PDP-11/20 assembler by Ken Thompson in 1971...
and may be used to operate the editor from a standard text terminal. By default, however, Sam presents its own Graphical User Interface
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
window, "samterm," which additionally allows point-and-click operations through Smalltalk
Smalltalk
Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
-80-style pop-up context menus. This two-process structure allowed sam to access files on networked host systems through remote execution of the file-access process while running the windowing interface locally, thereby bypassing latency over slow connections in its GUI
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
.
Samterm presents windows to files being edited and to at least one persistent command window which accepts input as sam commands. Most common editing operations are quickly and naturally accomplished with the point-and-click interface, which also functions inside the command window. This latter fact allows commands to be edited (and resubmitted) just as any other text, a function inherited from the DMD 5620 terminal interface.
Sam's command syntax is formally similar to ed
Ed (text editor)
ed is a line editor for the Unix operating system. It was one of the first end-user programs hosted on the system and has been standard in Unix-based systems ever since. ed was originally written in PDP-11/20 assembler by Ken Thompson in 1971...
's or ex
Ex (text editor)
ex, short for EXtended, is a line editor for Unix systems.The original ex was an advanced version of the standard Unix editor ed, included in the Berkeley Software Distribution...
's, containing (structural-) regular-expression-based conditional and loop functions and scope addressing, even sharing some of ed's syntax for such functions. But while ed's commands are line-oriented, sam's are selection-oriented. Selections are contiguous strings of text (which may span multiple lines), and are specified either with the mouse (by "sweeping" it over a region of text) or by a pattern match
Pattern matching
In computer science, pattern matching is the act of checking some sequence of tokens for the presence of the constituents of some pattern. In contrast to pattern recognition, the match usually has to be exact. The patterns generally have the form of either sequences or tree structures...
. Sam's commands take such selections as basic—more or less as other Unix tools treat lines; thus, multi-line and sub-line patterns are as naturally handled by Sam as whole-line patterns are by ed, vi
Vi
vi is a screen-oriented text editor originally created for the Unix operating system. The portable subset of the behavior of vi and programs based on it, and the ex editor language supported within these programs, is described by the Single Unix Specification and POSIX.The original code for vi...
, awk, Perl, etc. This is implemented through a model called "structural regular expressions," which can recursively apply regular-expression matching to obtain other (sub)selections within a given selection. In this way, sam's command set can be applied to substrings that are identified by arbitrarily complex context.
Sam extends its basic text-editing command set to handling of multiple files, providing similar pattern-based conditional and loop commands for filename specification. Any sequence of text-editing commands may be applied as a unit to each such specification.
Sam was one of the first text editors to support "infinite" undo
Undo
Undo is a command in many computer programs. It erases the last change done to the document reverting it to an older state. In some more advanced programs such as graphic processing, undo will negate the last command done to the file being edited....
to revert any number of editing errors. This feature, combined with Sam's facility to easily edit its own commands and, fundamentally, its small, orthogonal command set (containing only 33 commands), represent the program's bias toward a low learning threshold over other more expressive "power editors."
Sam is the preferred text editor of many eminent computer scientists; it replaced ed as Ken Thompson's favorite text editor, and he still uses it to this day. Sam is the text editor used by Bjarne Stroustrup
Bjarne Stroustrup
Bjarne Stroustrup ; born December 30, 1950 in Århus, Denmark) is a Danish computer scientist, most notable for the creation and the development of the widely used C++ programming language...
and Brian Kernighan
Brian Kernighan
Brian Wilson Kernighan is a Canadian computer scientist who worked at Bell Labs alongside Unix creators Ken Thompson and Dennis Ritchie and contributed to the development of Unix. He is also coauthor of the AWK and AMPL programming languages. The 'K' of K&R C and the 'K' in AWK both stand for...
. Others, like Dennis Ritchie
Dennis Ritchie
Dennis MacAlistair Ritchie , was an American computer scientist who "helped shape the digital era." He created the C programming language and, with long-time colleague Ken Thompson, the UNIX operating system...
, had moved on to use acme
Acme (text editor)
Acme is a text editor and graphical shell from the Plan 9 from Bell Labs operating system, designed and implemented by Rob Pike. It can use the sam command language. The design of the interface was influenced by Oberon. It is different from other editing environments in that it acts as a 9P server...
instead.
Sam vs. acme editor wars occur in the Plan 9
Plan 9 from Bell Labs
Plan 9 from Bell Labs is a distributed operating system. It was developed primarily for research purposes as the successor to Unix by the Computing Sciences Research Center at Bell Labs between the mid-1980s and 2002...
community (both are shipped with Plan 9) although both stem from a similar aesthetic bias. (In fact, both were written by Rob Pike.)
The latest incarnation of sam was written as part of the Plan 9 operating system, but there are Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and X Window System
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
ports available.
See also
- acme (text editor)Acme (text editor)Acme is a text editor and graphical shell from the Plan 9 from Bell Labs operating system, designed and implemented by Rob Pike. It can use the sam command language. The design of the interface was influenced by Oberon. It is different from other editing environments in that it acts as a 9P server...
— Rob Pike's other popular text editor and successor of sam. - ed (text editor)Ed (text editor)ed is a line editor for the Unix operating system. It was one of the first end-user programs hosted on the system and has been standard in Unix-based systems ever since. ed was originally written in PDP-11/20 assembler by Ken Thompson in 1971...
— The original Unix text editor by Ken Thompson - Plan 9 from Bell LabsPlan 9 from Bell LabsPlan 9 from Bell Labs is a distributed operating system. It was developed primarily for research purposes as the successor to Unix by the Computing Sciences Research Center at Bell Labs between the mid-1980s and 2002...
- List of Unix programs