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Full Discussion: awk removing data before or after a pattern
Top Forums Shell Programming and Scripting awk removing data before or after a pattern Post 302443394 by agama on Sunday 8th of August 2010 03:42:12 PM
Old 08-08-2010
This is one way to accomplish what you need; may not be the most efficient, but is easy to understand. It will do both 'drop before' and 'drop after' functions. I've set it up to match strings, not patterns, if you truly need to match patterns, use the match() function in awk rather than index().

Code:
#!/usr/bin/env ksh

# parms:        $1 -- before string; all records before matching this string are dropped
#                       If this is "none" then all records until the after string is matched are kept
#               $2 -- after string; all records after this string are dropped.

awk -v toss_before="${1:-none}" -v toss_after="$2" '
        BEGIN {
                if( toss_before == "none" )     # keep everything from the start
                        snarf = 1;
                else
                        snarf = 0;              # must wait until we see toss_before to start keeping data
        }

        {
                if( snarf ) 
                {
                        printf( "%s\n", $0 );           # print if snarfing 

                        if( toss_after && index( $0, toss_after ) )     # check to see if this has the end string
                                exit( 0 );
                }
                else                                    # not snarfing, see if this is the start string
                {
                        if( index( $0, toss_before ) )
                        {
                                printf( "%s\n", $0 );
                                snarf = 1;
                        }
                }
        }
'

 

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LEARN ABOUT PLAN9

char

CHAR(1) 						      General Commands Manual							   CHAR(1)

NAME

       char, 1/2char, rschar - browse the Unicode Standard

SYNOPSIS

       char [ font ]
       1/2char [ -s file ] [ font ]
       rschar [ -bgj ] [ -s file ] [ font ]

DESCRIPTION

       Char  displays  two square arrays of characters on the screen.  The left square shows the first character of each 256-character page of the
       Unicode Standard.  The right square shows the contents of one page.  Using button 1 or 2 to select a character in the left  square  changes
       the  right  square  to  display the corresponding page and displays the offset and name of the page in the upper left corner of the screen.
       Selecting a character in the right square displays its hexadecimal value and name.  In addition, any characters selected with button 2  are
       added  to the end of 81/2's snarf buffer.  Button 3 pops up a menu containing an exit button, whose selection must be confirmed by pressing
       button 3 again and a clear snarf button that empties the snarf buffer.

       The optional argument indicates which font to use (default $font).

       1/2char is intended for a smaller window and displays only a single 256-character panel.  Clicking button 1 on  a  character  displays  its
       code  and, if possible, description; button 2 works similarly, but also writes the character to file, default /dev/snarf (81/2's snarf buf-
       fer), which it displays near the bottom of the window.  Clicking button 3 selects the page corresponding to  the  cursor  position  in  the
       panel.  Typed characters are added to the file, except: backspace deletes the last character; control-U clears the buffer; control-D exits.

       Rschar  is  the radical/stroke chart from Volume 2 of the Unicode Standard.  Flags can be used to restrict the display to one or more Asian
       character sets:

       -b     Big Five (traditional Chinese).

       -g     GB 2312-80 (simplified Chinese).

       -j     JIS X 0208-1990 (Japanese).

       By default, all characters are shown.  Button 3 controls a menu to change flag selections.  Radicals are shown in a panel on the left  side
       of  the	window.   Clicking on a radical with button 1 or 2 brings up, on the right, a panel of characters ordered by stroke count.  If the
       window is too small to contain them all, one may scroll through successive panels by clicking on arrows that appear at the  top.   Clicking
       on  a character with button 1 displays its code; clicking with button 2 adds the character to the snarf buffer.	Typed characters behave as
       in 1/2char.

FILES

       /lib/unicode contains the names of the unicode characters.  Many characters have no name.

SOURCE

       /sys/src/cmd/char.c
       /sys/src/cmd/1/2char.c
       /sys/src/cmd/rschar

SEE ALSO

       81/2(1), 81/2(4)

BUGS

       Char needs a largish window to work properly and doesn't complain if it doesn't get it.

																	   CHAR(1)
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