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Top Forums Shell Programming and Scripting Grep with regex containing one string but not the other Post 302940848 by Corona688 on Thursday 9th of April 2015 12:21:15 PM
Old 04-09-2015
Greedy matching is doing you in. All "(?!foobuzz)..." needs to find is one spot before user1 which doesn't start in 'f' and its condition is satisfied. The .* after it swallows everything. So it scans the first character, goes 'yay its not foobuzz', searches for the username and accepts.

So, you need to force the regex to check for (?!foobuzz) in a relevant spot. Right after a | character perhaps. And you have to make it check all of them so it won't cheat by skipping ahead.

You can match entire fields with [^|]*\|, and force them to not start with foobuzz via (?!foobuzz)[^|]*\|, match several in a row by wrapping it in ()* and force it to start at the beginning of the line with ^.

So ^((?!foobuzz)[^|]*\|)*UserID1 will only accept a line containing zero or more | fields, none of which begin with foobuzz, after which it must immediately find 'userid1'.

Code:
$ printf "2015-04-08 19:04:56,157|yyyyyyyyyy|          |foobuzz|          |INFO |REQUEST|UserID1:23 | ohnooo\n" |
        grep -P '^((?!foobuzz)[^|]*\|)*UserID1'

$ printf "2015-04-08 19:04:56,157|yyyyyyyyyy|          |frobuzz|          |INFO |REQUEST|UserID1:23 | ohnooo\n" | grep -P '^((?!foobuzz)[^|]*\|)*UserID1'
2015-04-08 19:04:56,157|yyyyyyyyyy|          |frobuzz|          |INFO |REQUEST|UserID1:23 | ohnooo

I don't think rewriting it in awk or sed would necessarily make it slower, but if you have a big pile of regexes already, could be a painful amount of work.

Last edited by Corona688; 04-09-2015 at 01:29 PM..
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GREP(1) 						      General Commands Manual							   GREP(1)

NAME
grep, g - search a file for a pattern SYNOPSIS
grep [ option ... ] pattern [ file ... ] g [ option ... ] pattern [ file ... ] DESCRIPTION
Grep searches the input files (standard input default) for lines that match the pattern, a regular expression as defined in regexp(7) with the addition of a newline character as an alternative (substitute for |) with lowest precedence. Normally, each line matching the pattern is `selected', and each selected line is copied to the standard output. The options are -c Print only a count of matching lines. -h Do not print file name tags (headers) with output lines. -e The following argument is taken as a pattern. This option makes it easy to specify patterns that might confuse argument parsing, such as -n. -i Ignore alphabetic case distinctions. The implementation folds into lower case all letters in the pattern and input before interpre- tation. Matched lines are printed in their original form. -l (ell) Print the names of files with selected lines; don't print the lines. -L Print the names of files with no selected lines; the converse of -l. -n Mark each printed line with its line number counted in its file. -s Produce no output, but return status. -v Reverse: print lines that do not match the pattern. -f The pattern argument is the name of a file containing regular expressions one per line. -b Don't buffer the output: write each output line as soon as it is discovered. Output lines are tagged by file name when there is more than one input file. (To force this tagging, include /dev/null as a file name argument.) Care should be taken when using the shell metacharacters $*[^|()= and newline in pattern; it is safest to enclose the entire expression in single quotes '...'. An expression starting with '*' will treat the rest of the expression as literal characters. G invokes grep with -n and forces tagging of output lines by file name. If no files are listed, it searches all files matching *.C *.b *.c *.h *.m *.cc *.java *.cgi *.pl *.py *.tex *.ms SOURCE
/src/cmd/grep /bin/g SEE ALSO
ed(1), awk(1), sed(1), sam(1), regexp(7) DIAGNOSTICS
Exit status is null if any lines are selected, or non-null when no lines are selected or an error occurs. GREP(1)
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