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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grep

GREP(1) 						      General Commands Manual							   GREP(1)

NAME

       grep - search a file for a pattern

SYNOPSIS

       grep [ option ...  ] pattern [ file ...	]

DESCRIPTION

       Grep  searches  the input files (standard input default) for lines (with newlines excluded) that match the pattern, a regular expression as
       defined in regexp(6).  Normally, each line matching the pattern is `selected', and each selected line is copied	to  the  standard  output.
       The options are

       -c     Print only a count of matching lines.
       -h     Do not print file name tags (headers) with output lines.
       -i     Ignore alphabetic case distinctions.  The implementation folds into lower case all letters in the pattern and input before interpre-
	      tation.  Matched lines are printed in their original form.
       -l     (ell) Print the names of files with selected lines; don't print the lines.
       -L     Print the names of files with no selected lines; the converse of -l.
       -n     Mark each printed line with its line number counted in its file.
       -s     Produce no output, but return status.
       -v     Reverse: print lines that do not match the pattern.

       Output lines are tagged by file name when there is more than one input file.  (To force this tagging, include  /dev/null  as  a	file  name
       argument.)

       Care should be taken when using the shell metacharacters $*[^|()= and newline in pattern; it is safest to enclose the entire expression in
       single quotes '...'.

SOURCE

       /sys/src/cmd/grep.c

SEE ALSO

       ed(1), awk(1), sed(1), sam(1), regexp(6)

DIAGNOSTICS

       Exit status is null if any lines are selected, or non-null when no lines are selected or an error occurs.

																	   GREP(1)