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Full Discussion: | help | unix | grep (GNU grep) 2.5.1 | advanced regex syntax
Top Forums UNIX for Dummies Questions & Answers | help | unix | grep (GNU grep) 2.5.1 | advanced regex syntax Post 302362244 by MykC on Thursday 15th of October 2009 10:52:33 AM
Old 10-15-2009
Ok, cool. You gave me some insight. For reference, the below line returns lines with exactly 3 matches if 'x' in the entire line.
3 can be replaced with any positive integer.
'x' can be replaced by any string.

Code:
grep "^\([^x]*x\)\{3\}[^x]*$" /usr/share/dict/words
grep -E "^([^x]*x){3}[^x]*$" /usr/share/dict/words

Addinging the option -E allowed to removed the "\" for the special characters and the code worked as expected.
There is also -P option for Perl extensions.

Code:
grep -E "^(?:[^x]*x){3}[^x]*$" /usr/share/dict/words
grep -P "^(?:[^x]*x){3}[^x]*$" /usr/share/dict/words

-E returned nothing when I added the ?: to ()
-P returned everything

I'm getting closer, I'll just need sometime to fool around with it. Thanks for the help.

Regular Expression Reference - Advanced Syntax
UNIX man pages : grep ()
 

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LEARN ABOUT SUSE

look

LOOK(1) 						    BSD General Commands Manual 						   LOOK(1)

NAME

     look -- display lines beginning with a given string

SYNOPSIS

     look [-dfa] [-t termchar] string [file]

DESCRIPTION

     The look utility displays any lines in file which contain string as a prefix.  As look performs a binary search, the lines in file must be
     sorted (where sort(1) got the same options -d and/or -f that look is invoked with).

     If file is not specified, the file /usr/share/dict/words is used, only alphanumeric characters are compared and the case of alphabetic char-
     acters is ignored.

     Options:

     -d      Dictionary character set and order, i.e. only alphanumeric characters are compared. (On by default if no file specified).

     -f      Ignore the case of alphabetic characters. (On by default if no file specified).

     -a      Use the alternate dictionary /usr/share/dict/web2

     -t      Specify a string termination character, i.e. only the characters in string up to and including the first occurrence of termchar are
	     compared.

     The look utility exits 0 if one or more lines were found and displayed, 1 if no lines were found, and >1 if an error occurred.

FILES

     /usr/share/dict/words  the dictionary
     /usr/share/dict/web2   the alternate dictionary

SEE ALSO

     grep(1), sort(1)

COMPATIBILITY

     The original manual page stated that tabs and blank characters participated in comparisons when the -d option was specified.  This was incor-
     rect and the current man page matches the historic implementation.

HISTORY

     Look appeared in Version 7 AT&T Unix.

AVAILABILITY

     The look command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.

BSD
								   June 14, 1993							       BSD
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