Remove x lines form top and y lines form bottom using AWK? Post: 302724659

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Top Forums Shell Programming and Scripting Remove x lines form top and y lines form bottom using AWK? Post 302724659 by cfajohnson on Thursday 1st of November 2012 06:03:19 AM

11-01-2012

Registered User

Code:

## NAME: topntail
## USAGE: topntail [-b N] [-e N] [FILE ...]

b=1  ## No. of lines to remove from beginning
e=1  ## No. of lines to remove from end

## Parse command-line options
while getopts b:e: opt
do
  case $opt in
      b) b=$OPTARG ;;  ## Number of lines to remove from beginning
      e) e=$OPTARG ;;  ## Number of lines to remove from end
  esac
done
shift $(( $OPTIND - 1 ))

case $b$e in   ## check for non-numeric characters in $b and $e
    *[!0-9]*) exit 5 ;;
esac

if [ $e -eq 0 ]
then
  sed "1,${b}d" "$@"  ## just remove from the top
else
  ## The buf[] array is a rotating buffer which contains the last N lines
  ## where N is the number of lines to be removed from the bottom of the file
  ## Printing starts when the line number is equal to the sum of the number
  ## of lines to be removed from top and bottom, and continues to the end
  ## of the file; the earliest line in the buffer is printed.
  ## The last N lines will not be printed.
  awk 'NR > b + e { print buf[ NR % e ] }
                  { buf[ NR % e ] = $0 }' b=$b e=$e "$@"
fi

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LEARN ABOUT REDHAT

prunehistory

PRUNEHISTORY(8) 					      System Manager's Manual						   PRUNEHISTORY(8)

NAME

       prunehistory - remove file names from Usenet history file

SYNOPSIS

       prunehistory [ -f filename ] [ -p ]

DESCRIPTION

       Prunehistory  modifies  the  history(5)	text file to ``remove'' a set of filenames from it.  The filenames are removed by overwriting them
       with spaces, so that the size and position of any following entries does not change.

       Prunehistory reads the standard input.  The input is taken as a set of lines.  Blank lines and lines starting with a  number  sign  (``#'')
       are ignored.  All other lines are should consist of a Message-ID followed by zero or more filenames.

       The  Message-ID	is  used as the dbz(3) key to get an offset into the text file.  If no filenames are mentioned on the input line, then all
       filenames in the text are ``removed.''  If any filenames are mentioned, they are converted into the history file notation.  If they  appear
       in the line for the specified Message-ID then they are removed.

       Since innd(8) only appends to the text file, prunehistory does not need to have any interaction with it.

OPTIONS

       -p     Prunehistory will normally complain about lines that do not follow the correct format.  If the ``-p'' flag is used, then the program
	      will silently print any invalid lines on its standard output.  (Blank lines and comment lines are also passed through.)  This can be
	      useful when prunehistory is used as a filter for other programs such as reap.

       -f     The default name of the history file is <pathdb in inn.conf>/history; to specify a different name, use the ``-f'' flag.

HISTORY

       Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  This is revision 1.7, dated 1998/04/09.

SEE ALSO

       dbz(3), history(5), inn.conf(5), innd(8).

																   PRUNEHISTORY(8)