lastnpages

早期freebsd实现

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Article: 26492 of comp.unix.questions
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From: [e-mail] (Michael D Brennan)
Newsgroups: comp.unix.questions
Subject: Re: How to print last <n> pages of a file
Message-ID: <[e-mail]>
Date: 6 May 91 15:42:00 GMT
Article-I.D.: ssc-bee.3948
Organization: Boeing Aerospace & Electronics, Seattle WA
Lines: 33


The following shell & (new) awk program prints the last n pages.

If you get more than 65 lines to a page, the program that inserts
the ^L's should be fixed.

-------------------------------------------------------------
#!/bin/sh
# usage: lastpages   --  prints 1 page reads stdin
#        lastpages  n -- prints  n pages reads stdin
#        lastpages  n  files -- prints n pages, reads file list

program='BEGIN{RS = ORS = "\f" }


{ page[NR] = $0 
  if ( NR > numpages )  delete  page[NR-numpages]
}

END { 
  i = NR - numpages + 1
  if ( i <= 0 ) i = 1

  while( i <= NR )  print page[i++]
}'


case $# in 
0)  awk "$program" numpages=1 - ;;
1)  awk "$program" numpages=$1 - ;;
*)  pages=$1 ; shift
    awk "$program" numpages=$pages  $* ;;
esac