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Top Forums UNIX for Dummies Questions & Answers Finding lines with a regular expression, replacing them with blank lines Post 302644675 by Golpette on Tuesday 22nd of May 2012 09:01:15 AM
Old 05-22-2012
Finding lines with a regular expression, replacing them with blank lines

So the tag for this forum says all newbies welcome...
All I want to do is go through my file and find lines which contain a given string of characters then replace these with a blank line. I really tried to find a simple command to do this but failed.

Here's what I did come up with though:

Code:
sed -e 's/REGEXP[^ ]*/MARKER/g' -e 's/[^ ]*MARKER//g' in.txt > out.txt

So I find a REGEXP, replace that and the rest of the line with "MARKER", then I replace the start of the line, including "MARKER" with nothing, thus leaving behind a blank entry...

I think this has worked... Better method please?!
 

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EXPR(1) 								FSF								   EXPR(1)

NAME
expr - evaluate expressions SYNOPSIS
expr EXPRESSION expr OPTION DESCRIPTION
--help display this help and exit --version output version information and exit Print the value of EXPRESSION to standard output. A blank line below separates increasing precedence groups. EXPRESSION may be: ARG1 | ARG2 ARG1 if it is neither null nor 0, otherwise ARG2 ARG1 & ARG2 ARG1 if neither argument is null or 0, otherwise 0 ARG1 < ARG2 ARG1 is less than ARG2 ARG1 <= ARG2 ARG1 is less than or equal to ARG2 ARG1 = ARG2 ARG1 is equal to ARG2 ARG1 != ARG2 ARG1 is unequal to ARG2 ARG1 >= ARG2 ARG1 is greater than or equal to ARG2 ARG1 > ARG2 ARG1 is greater than ARG2 ARG1 + ARG2 arithmetic sum of ARG1 and ARG2 ARG1 - ARG2 arithmetic difference of ARG1 and ARG2 ARG1 * ARG2 arithmetic product of ARG1 and ARG2 ARG1 / ARG2 arithmetic quotient of ARG1 divided by ARG2 ARG1 % ARG2 arithmetic remainder of ARG1 divided by ARG2 STRING : REGEXP anchored pattern match of REGEXP in STRING match STRING REGEXP same as STRING : REGEXP substr STRING POS LENGTH substring of STRING, POS counted from 1 index STRING CHARS index in STRING where any CHARS is found, or 0 length STRING length of STRING + TOKEN interpret TOKEN as a string, even if it is a keyword like `match' or an operator like `/' ( EXPRESSION ) value of EXPRESSION Beware that many operators need to be escaped or quoted for shells. Comparisons are arithmetic if both ARGs are numbers, else lexicograph- ical. Pattern matches return the string matched between ( and ) or null; if ( and ) are not used, they return the number of characters matched or 0. AUTHOR
Written by Mike Parker. REPORTING BUGS
Report bugs to <bug-coreutils@gnu.org>. COPYRIGHT
Copyright (C) 2002 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU- LAR PURPOSE. SEE ALSO
The full documentation for expr is maintained as a Texinfo manual. If the info and expr programs are properly installed at your site, the command info expr should give you access to the complete manual. GNU coreutils 4.5.3 February 2003 EXPR(1)
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