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Top Forums Shell Programming and Scripting Going mad on an egrep command (Reg Expressions) Post 303019456 by Donzo on Friday 29th of June 2018 12:36:35 PM
Old 06-29-2018
Going mad on an egrep command (Reg Expressions)

Dear community,


I am trying for several hours now to create an egrep command to grep the number of lines containing a specific text from a text-file but seem to have an error somewhere.


The Textfile contains several thousand lines and has the expression "Lastname" in several lines. Problem is, that there is also expressions like "xLastname" or "abcLastname" in there which I DON'T want to grab.
So the definition of the RegExpression should look like this

EITHER there is no text at all in the line before "Lastname" appears
OR there is Text in the line BUT then a SPACE has to be between the random text and the expression "Lastname"


I tried with ((.+\ )?|(^.))Lastname and ((.+\ )?|(^.*))Lastname and ((.+\ )?|[^.])Lastname and ((.+\ )?|[^.*])Lastname but it always results in the egrep command finding expressions like "abcLastname".


Where is my mistake? The first part (.+\ ) ("If there is text, there HAS to be a SPACE afterwards") seems to work fine but the "OR there is no text at all" does not seem to work.
Wasn't there a special character that I can use to simply check if whatever comes after it is the FIRST expression/character in the line? I cannot find that information online unfortunately.


Thanks to all of you in advance for your help


Best Regards
Donzo

Last edited by Donzo; 06-29-2018 at 02:03 PM..
 
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ZGREP(1)						    BSD General Commands Manual 						  ZGREP(1)

NAME
zgrep, zegrep, zfgrep -- print lines matching a pattern in gzip-compressed files SYNOPSIS
zgrep [grep-flags] [--] pattern [files ...] zegrep [grep-flags] [--] pattern [file ...] zfgrep [grep-flags] [--] pattern [file ...] DESCRIPTION
zgrep runs grep(1) on files or stdin, if no files argument is given, after decompressing them with zcat(1). The grep-flags and pattern arguments are passed on to grep(1). If an -e flag is found in the grep-flags, zgrep will not look for a pattern argument. zegrep calls egrep(1), while zfgrep calls fgrep(1). EXIT STATUS
In case of missing arguments or missing pattern, 1 will be returned, otherwise 0. SEE ALSO
egrep(1), fgrep(1), grep(1), gzip(1), zcat(1) AUTHORS
Thomas Klausner <wiz@NetBSD.org> BSD
December 28, 2003 BSD

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