On Friday 05 February 2010 14:47:21 Stephen Powell wrote: > On Fri, 5 Feb 2010 12:42:47 -0500 (EST), Bob McGowan wrote: > Let me give you a > simple example of a CMS pipeline for illustrative purposes, > so that you will get some idea of what I'm talking about. > [snip: Long, but very useful description.] > This pipeline can be illustrated graphically as follows: > > +---+ +-------+ +--------+ +----------+ +---+ > |-| < |-->| NFIND |-->| LOCATE |------>| FANINANY |-->| > |-| > +---+ +-------+ +--------+ 1 1 +----------+ +---+ > | 2 | 2 > V A > | +--------+ | > LOCM:-->| LOCATE |-->-FIN: > +--------+ mkfifo "LOCM" && mkfifo "FIN" && ( "<" | "NFIND" | "LOCATE" 2> "LOCM" | "FANINANY" 2< "FIN"| ">" & "LOCATE" < "LOCM" > "FIN" & wait ) People with more shell magic than me might be able to simplify that to not use fifos, but I figured they were fair game since you get stream labels. (That's basically all a fifo is.) Technically speaking, that's all one command, per the Single UNIX Specifation. It matches the shell grammar start symbol "complete_command" documented <http://www.opengroup.org/onlinepubs/007908775/xcu/chap2.html#tag_001_010_002>. So, basically, we have different basic building blocks (I don't know a grep variant that acts like LOCATE, for example), but the larger structure is very similar. Most UNIX/Linux utilities for the command line assume all input on fd 0, all normal output on fd 1, and end-user notifications written to fd 2. However, there's nothing actively preventing binaries from reading from fd 2, writing to fd 0, or expecting i/o on fds 3 through 9. (IIRC, anything greater than 9 is reserved when using the shell.) -- Boyd Stephen Smith Jr. ,= ,-_-. =. bss@iguanasuicide.net ((_/)o o(\_)) ICQ: 514984 YM/AIM: DaTwinkDaddy `-'(. .)`-' http://iguanasuicide.net/ \_/
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