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Full Discussion: Conditionally delete last X lines
Top Forums Shell Programming and Scripting Conditionally delete last X lines Post 302496361 by honglus on Sunday 13th of February 2011 09:03:06 PM
Old 02-13-2011
I figured it out, But I don't like the trick of tac.
[Help still needed, Solaris doesn't have tac command.]

Code:
$cat t2
test1
test2
[23] remove1 
test3
[24] remove2
[1] remove

$tac t2 | awk '{ if (($0 ~ /^\[[0-9]+\]/ )&&( flag!=1 )) { } else {print $0; flag=1 } } ' | tac
test1
test2
[23] remove1 
test3

Last edited by honglus; 02-14-2011 at 12:18 AM..
 

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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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