l5.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

#print
		    More Alteration - Filtering

   One of the most convenient and powerful features of vi is the ability
to take parts of your text and run it through a program.  This is called
'filtering' and is quite commonly used with programs like nroff, fmt,
spell, sort, uniq, and others.  It is much more convenient to use this
than to write a portion of the file out, leave the editor, run the program
on that portion into a temporary file, re-enter the editor, and read in
the contents of the temporary file.

   The filtering command in vi is '!' and it can take any targets that the
'd', 'c', 'y', '>', or '<' commands can.  Thus, to run your whole text
through nroff, you would simply type
	1G	To go to the very beginning of the file
	!G	To filter the whole file through a program.  Vi will prompt
		with a '!' at the bottom of screen.   You type
	nroff	and hit return and whammo, off it goes.  Your file will be
		replaced by the nroff output.  Use the undo command to go
		back to the original text afterwards if you wish.

   Type 'ready' to try out this command.
#user
#create FilterTest
EXERCISE
	Use the ! command to run the part of this file below the dashed line
through the program 'sort'.  When you've done that, delete all of these
instructions, upto and including the dashed line.  Then exit, saving your
changes.
-----------------------------------------------------------------------------
to.vax135
net.bugs.v7
net.rec.scuba
net.columbia
net.games.trivia
net.trivia
net.oa
net.news.b
net.applic
net.music
net.misc
fa.arms-d
fa.railroad
fa.arpa-bboard
cu.bboard
net.bugs.2bsd
net.bugs.4bsd
fa.space
net.space
net.eunice
net.rec.bridge
net.cycle
cu.games.empire
net.cse
net.news.newsite
net.games.rogue
net.rec.skydive
cu.info-bitgraph
net.math
fa.poli-sci
net.general
cu.general
net.travel
net.sport.baseball
to.cornell
net.lang.apl
net.dcom
fa.telecom
fa.info-cpm
net.lang
net.games.pacman
net.aviation
net.ham-radio
fa.info-micro
net.info-micro
net.micro
net.rec.photo
net.auto
fa.editor-p
fa.digest-p
fa.tcp-ip
cu.tcp-ip
net.games.dip
net.games.frp
net.lang.lisp
net.lisp
net.news.group
cu.msggroup
net.followup
cu.followup
net.jokes.q
net.rumor
net.ucds
net.unix-wizards
net.rec.birds
net.records
net.sources
net.movies
net.jokes
net.games
cu.games
net.wines
net.taxes
net.bugs
net.periphs
net.cooks
fa.works
net.works
cu.works
net.cms
fa.info-terms
cu.info-terms
fa.sf-lovers
net.sf-lovers
net.chess
fa.human-nets
cu.localnets
net.news
cu.info-pcnet
net.test
net.auto.vw
fa.info-vax
cu.info-vax
net.usenix
net.unix
net.sport.hockey
fa.energy
#create SortedList
cu.bboard
cu.followup
cu.games
cu.games.empire
cu.general
cu.info-bitgraph
cu.info-pcnet
cu.info-terms
cu.info-vax
cu.localnets
cu.msggroup
cu.tcp-ip
cu.works
fa.arms-d
fa.arpa-bboard
fa.digest-p
fa.editor-p
fa.energy
fa.human-nets
fa.info-cpm
fa.info-micro
fa.info-terms
fa.info-vax
fa.poli-sci
fa.railroad
fa.sf-lovers
fa.space
fa.tcp-ip
fa.telecom
fa.works
net.applic
net.auto
net.auto.vw
net.aviation
net.bugs
net.bugs.2bsd
net.bugs.4bsd
net.bugs.v7
net.chess
net.cms
net.columbia
net.cooks
net.cse
net.cycle
net.dcom
net.eunice
net.followup
net.games
net.games.dip
net.games.frp
net.games.pacman
net.games.rogue
net.games.trivia
net.general
net.ham-radio
net.info-micro
net.jokes
net.jokes.q
net.lang
net.lang.apl
net.lang.lisp
net.lisp
net.math
net.micro
net.misc
net.movies
net.music
net.news
net.news.b
net.news.group
net.news.newsite
net.oa
net.periphs
net.rec.birds
net.rec.bridge
net.rec.photo
net.rec.scuba
net.rec.skydive
net.records
net.rumor
net.sf-lovers
net.sources
net.space
net.sport.baseball
net.sport.hockey
net.taxes
net.test
net.travel
net.trivia
net.ucds
net.unix
net.unix-wizards
net.usenix
net.wines
net.works
to.cornell
to.vax135
#
vi FilterTest
#cmp FilterTest SortedList
#succeed
Quite impressive!  And you should be impressed too, at how simple it was to
do that.   Now you're good enough to go on to the tricky stuff...
#fail
Not quite.  What you need to do is to move the cursor to the first line
after the dashed line.  Then type '!G' (to tell vi you want to pipe the rest
of the file through a program).  Vi will prompt at the bottom of the screen
and you type 'sort' and hit return.  After a moment, the old, unsorted list
should be replaced by a brand spanking new sorted one (hopefully of the same
elements).  You then go back and delete the instructions (all of them, through
the dashed line) using the 'dd' command and Voila!, you're done.  Just type
:wq to save your changes and exit.

When the learn program types a percent sign, just type 'ready' to try it again.
#next
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