Influence
The C shell was extremely successful in introducing a large number of innovations including the history mechanism, aliases, tilde notation, interactive filename completion, an expression grammar built into the shell, and more, that have since been copied by other Unix shells. But in contrast to sh, which has spawned a large number of independently-developed clones, including ksh and bash, only two csh clones are known. (Since tcsh was based on the csh code originally written by Bill Joy, it is not considered a clone.)
In 1986, Allen Holub wrote On Command: Writing a Unix-Like Shell for MS-DOS, a book describing a program he had written called "SH" but which in fact copied the language design and features of csh, not sh. Companion diskettes containing full source for SH and for a basic set of Unix-like utilities (cat, cp, grep, etc.) were available for $25 and $30, respectively, from the publisher. The control structures, expression grammar, history mechanism and other features in Holub's SH were identical to those of the C shell.
In 1988, Hamilton Laboratories began shipping Hamilton C shell, written by Nicole Hamilton, for OS/2. It included both a csh clone and a set of Unix-like utilities. In 1992, Hamilton C shell was released for Windows NT. The Windows version continues to be actively supported but the OS/2 version was discontinued in 2003. An early quick reference described the intent as "full compliance with the entire C shell language (except job control)" but with improvements to the language design and adaptation to the differences between Unix and a PC. The most important improvement was a top-down parser that allowed control structures to be nested or piped, something the original C shell could not support, given its ad hoc parser. Hamilton also added new language features including built-in and user-defined procedures, block-structured local variables and floating point arithmetic. Adaptation to a PC included support for the filename and other conventions on a PC and the use of threads instead of forks (which were not available under either OS/2 or Windows) to achieve parallelism, e.g., in setting up a pipeline.
C shell has been, and continues to be, the dominant scripting language in much of the speech recognition research community, and is closely associated with the HTK speech tools.
Read more about this topic: C Shell
Famous quotes containing the word influence:
“What do women want with votes, when they hold the sceptre of influence with which they can control even votes, if they wield it aright?”
—Mrs. H. O. Ward (1824–1899)
“Under the influence of fear, which always leads men to take a pessimistic view of things, they magnified their enemies’ resources, and minimized their own.”
—Titus Livius (Livy)
“Just what is the civil law? What neither influence can affect, nor power break, nor money corrupt: were it to be suppressed or even merely ignored or inadequately observed, no one would feel safe about anything, whether his own possessions, the inheritance he expects from his father, or the bequests he makes to his children.”
—Marcus Tullius Cicero (106–43 B.C.)