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Full Discussion: Simple awk search problem
Top Forums Shell Programming and Scripting Simple awk search problem Post 302580183 by mirni on Wednesday 7th of December 2011 10:01:40 PM
Old 12-07-2011
Well this
Code:
awk '/reg_exp/,0

has some syntax errors and wouldn't run.

How about a naive approach:
Code:
 awk '/regex/{flag=1;next}flag' input

EDIT: oops, I misread the part "after the last occurrence". Sorry

To find out that the occurrence is the last, awk has to search through the whole file. So you either need to scan through file twice (once in the BEGIN block, to find which is the last), or save the lines in an array, which may overflow your memory, if the file is really large. So I would make use of 'tac' which will print the lines in reverse order:

Code:
 tac lines | sed -n '/six/{q};p' | tac

Last edited by mirni; 12-07-2011 at 11:08 PM..
 

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LEARN ABOUT PLAN9

tac

TAC(1)                                                             User Commands                                                            TAC(1)

NAME

       tac - concatenate and print files in reverse

SYNOPSIS

       tac [OPTION]... [FILE]...

DESCRIPTION

       Write each FILE to standard output, last line first.

       With no FILE, or when FILE is -, read standard input.

       Mandatory arguments to long options are mandatory for short options too.

       -b, --before
              attach the separator before instead of after

       -r, --regex
              interpret the separator as a regular expression

       -s, --separator=STRING
              use STRING as the separator instead of newline

       --help display this help and exit

       --version
              output version information and exit

AUTHOR

       Written by Jay Lepreau and David MacKenzie.

REPORTING BUGS

       GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
       Report tac translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright (C) 2017 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       rev(1)

       Full documentation at: <http://www.gnu.org/software/coreutils/tac>
       or available locally via: info '(coreutils) tac invocation'

GNU coreutils 8.28                                                 January 2018                                                             TAC(1)
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