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Grep
grep is a command-line utility for searching plain-text data sets for lines that match a regular expression. Its name comes from the ed command ''g/re/p'' (''globally search for a regular expression and print matching lines''), which has the same effect. grep was originally developed for the Unix operating system, but later available for all Unix-like systems and some others such as OS-9. History Before it was named, grep was a private utility written by Ken Thompson to search files for certain patterns. Doug McIlroy, unaware of its existence, asked Thompson to write such a program. Responding that he would think about such a utility overnight, Thompson actually corrected bugs and made improvements for about an hour on his own program called s (short for "search"). The next day he presented the program to McIlroy, who said it was exactly what he wanted. Thompson's account may explain the belief that grep was written overnight. Thompson wrote the first version in PDP-11 asse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regular Expression
A regular expression (shortened as regex or regexp; sometimes referred to as rational expression) is a sequence of characters that specifies a search pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation. Regular expression techniques are developed in theoretical computer science and formal language theory. The concept of regular expressions began in the 1950s, when the American mathematician Stephen Cole Kleene formalized the concept of a regular language. They came into common use with Unix text-processing utilities. Different syntaxes for writing regular expressions have existed since the 1980s, one being the POSIX standard and another, widely used, being the Perl syntax. Regular expressions are used in search engines, in search and replace dialogs of word processors and text editors, in text processing utilities such as sed and AWK, and in lexical ana ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pgrep
pgrep is a command-line utility initially written for use with the Solaris 7 operating system by Mike Shapiro. It has since been available in illumos and reimplemented for the Linux and BSDs (DragonFly BSD, FreeBSD, NetBSD, and OpenBSD). It searches for all the named processes that can be specified as extended regular expression patterns, and—by default—returns their process ID. Alternatives include pidof (finds process ID given a program name) and ps. Example usage The default behaviour of pgrep (returning the process identifier of the named tasks) simplifies an otherwise complex task and is invoked with: $ pgrep 'bash' Which is roughly equivalent to: $ ps ax , awk ' $5 ~ /bash/ ' Additional functionality of pgrep is listing the process name as well as the PID (-l Lists the process name as well as the process ID) of all processes belonging to the group alice (-G Only match processes whose real group ID is listed. Either the numerical or symbolical value may be use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alfred Aho
Alfred Vaino Aho (born August 9, 1941) is a Canadian computer scientist best known for his work on programming languages, compilers, and related algorithms, and his textbooks on the art and science of computer programming. Aho was elected into the National Academy of Engineering in 1999 for his contributions to the fields of algorithms and programming tools. He and his long-time collaborator Jeffrey Ullman are the recipients of the 2020 Turing Award, generally recognized as the highest distinction in computer science. Career Aho received a B.A.Sc. (1963) in Engineering Physics from the University of Toronto, then an M.A. (1965) and Ph.D. (1967) in Electrical Engineering/Computer Science from Princeton University. He conducted research at Bell Labs from 1967 to 1991, and again from 1997 to 2002 as Vice President of the Computing Sciences Research Center. Since 1995, he has held the Lawrence Gussman Professorship in Computer Science at Columbia University. He served as chair of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filter (higher-order Function)
In functional programming, filter is a higher-order function that processes a data structure (usually a list) in some order to produce a new data structure containing exactly those elements of the original data structure for which a given predicate returns the boolean value true. Example In Haskell, the code example filter even ..10 evaluates to the list 2, 4, …, 10 by applying the predicate even to every element of the list of integers 1, 2, …, 10 in that order and creating a new list of those elements for which the predicate returns the boolean value true, thereby giving a list containing only the even members of that list. Conversely, the code example filter (not . even) ..10 evaluates to the list 1, 3, …, 9 by collecting those elements of the list of integers 1, 2, …, 10 for which the predicate even returns the boolean value false (with . being the function composition operator). Visual example Below, you can see a view of each step of the filter process f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley ( BSD), Microsoft ( Xenix), Sun Microsystems (SunOS/ Solaris), HP/ HPE (HP-UX), and IBM ( AIX). In the early 1990s, AT&T sold its rights in Unix to Novell, which then sold the UNIX trademark to The Open Group, an industry consortium founded in 1996. The Open Group allows the use of the mark for certified operating systems that comply with the Single UNIX Specification (SUS). Unix systems are characterized by a modular design that is sometimes called the " Unix philosophy". According to this p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ed (text Editor)
(pronounced as distinct letters, ) is a line editor for Unix and Unix-like operating systems. It was one of the first parts of the Unix operating system that was developed, in August 1969. It remains part of the POSIX and Open Group standards for Unix-based operating systems, alongside the more sophisticated full-screen editor vi. History and influence The ed text editor was one of the first three key elements of the Unix operating system— assembler, editor, and shell—developed by Ken Thompson in August 1969 on a PDP-7 at AT&T Bell Labs. Many features of ed came from the qed text editor developed at Thompson's alma mater University of California, Berkeley. Thompson was very familiar with qed, and had reimplemented it on the CTSS and Multics systems. Thompson's versions of qed were notable as the first to implement regular expressions. Regular expressions are also implemented in ed, though their implementation is considerably less general than that in qed. Denn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ken Thompson
Kenneth Lane Thompson (born February 4, 1943) is an American pioneer of computer science. Thompson worked at Bell Labs for most of his career where he designed and implemented the original Unix operating system. He also invented the B programming language, the direct predecessor to the C programming language, and was one of the creators and early developers of the Plan 9 operating system. Since 2006, Thompson has worked at Google, where he co-developed the Go programming language. Other notable contributions included his work on regular expressions and early computer text editors QED and ed, the definition of the UTF-8 encoding, and his work on computer chess that included the creation of endgame tablebases and the chess machine Belle. He won the Turing Award in 1983 with his long-term colleague Dennis Ritchie. Early life and education Thompson was born in New Orleans, Louisiana. When asked how he learned to program, Thompson stated, "I was always fascinated with logic an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MSX-DOS
MSX-DOS is a discontinued disk operating system developed by Microsoft for the 8-bit home computer standard MSX, and is a cross between MS-DOS 1.25 and CP/M-80 2. MSX-DOS MSX-DOS and the extended BASIC with 3½-inch floppy disk support were simultaneously developed by Microsoft and Spectravideo as a software and hardware standard for the MSX home computer standard, to add disk capabilities to BASIC and to give the system a cheaper software medium than Memory Cartridges, and a more powerful storage system than cassette tape. The standard BIOS of an unexpanded MSX computer did not have any floppy disk support, so the additional floppy disk expansion system came with its own BIOS extension ROM (built-in on the disk controller) called the BDOS. Spectravideo also released an MSX-DOS disk in conjunction with the SVI-707 which could be loaded into an MSX system. Once MSX-DOS has been loaded, the system searches the MSX-DOS disk for the COMMAND.COM file and loads it into memory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OS-9
OS-9 is a family of real-time, process-based, multitasking, multi-user operating systems, developed in the 1980s, originally by Microware Systems Corporation for the Motorola 6809 microprocessor. It was purchased by Radisys Corp in 2001, and was purchased again in 2013 by its current owner Microware LP. The OS-9 family was popular for general-purpose computing and remains in use in commercial embedded systems and amongst hobbyists. Today, OS-9 is a product name used by both a Motorola 68000-series machine language OS and a portable (PowerPC, x86, ARM, MIPS, SH4, etc.) version written in C, originally known as OS-9000. History The first version ("OS-9 Level One"), which dates back to 1979–1980, was written in assembly language for the Motorola 6809 CPU, and all of its processes ran within the 64KB address space of the CPU without a memory management unit. It was developed as a supporting operating system for the BASIC09 project, contracted for by Motorola as part of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plan 9 From Bell Labs
Plan 9 from Bell Labs is a distributed operating system which originated from the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s and built on UNIX concepts first developed there in the late 1960s. Since 2000, Plan 9 has been free and open-source. The final official release was in early 2015. Under Plan 9, UNIX's '' everything is a file'' metaphor is extended via a pervasive network-centric filesystem, and the cursor-addressed, terminal-based I/O at the heart of UNIX-like operating systems is replaced by a windowing system and graphical user interface without cursor addressing, although rc, the Plan 9 shell, is text-based. The name ''Plan 9 from Bell Labs'' is a reference to the Ed Wood 1957 cult science fiction Z-movie ''Plan 9 from Outer Space''. The system continues to be used and developed by operating system researchers and hobbyists. History Plan 9 from Bell Labs was originally developed, starting in the late 1980s, by members of the Comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Version 4 Unix
The term "Research Unix" refers to early versions of the Unix operating system for DEC PDP-7, PDP-11, VAX and Interdata 7/32 and 8/32 computers, developed in the Bell Labs Computing Sciences Research Center (CSRC). History The term ''Research Unix'' first appeared in the Bell System Technical Journal (Vol. 57, No. 6, Pt. 2 Jul/Aug 1978) to distinguish it from other versions internal to Bell Labs (such as PWB/UNIX and MERT) whose code-base had diverged from the primary CSRC version. However, that term was little-used until Version 8 Unix, but has been retroactively applied to earlier versions as well. Prior to V8, the operating system was most commonly called simply UNIX (in caps) or the UNIX Time-Sharing System. AT&T licensed Version 5 to educational institutions, and Version 6 also to commercial sites. Schools paid $200 and others $20,000, discouraging most commercial use, but Version 6 was the most widely used version into the 1980s. Research Unix versions are often referr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
