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Grouping in grep

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http://www.unix.com – How do you do grouping in grep? Here's how I tried it at first: Code: egrep ’qualit(y|ies)’ /usr/share/dict/words -bash: syntax error near unexpected token `(' I'm using GNUgrep, and I found this on their site. grep regular expression syntax Quote: Grouping is performed with backslashes followed by parentheses ‘\(’, ‘\)’. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example ‘\2’ matches the second group expression. The order of group expressions (HowTos)

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Submitted by robot1 on 06/19/2012 – Made popular on 06/19/2012

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Hi all, Accounting to gnu/sed manual, http://www.gnu.org/software/sed/manu...ar-Expressions * Matches a sequence of zero or more instances of matches for the preceding regular expression, which must be an ordinary character, a special character preceded by \, a ., a grouped regexp (see below), or a bracket expression.

TweetGrep is one of the most important tools for a shell user. When it comes to retrieving required data from a bulk of text, grep is your best bet. Its very flexible, powerful and as I came to know today, has an interesting story too. It all started a long time ago.

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grep: invalid content of \{\} 12 weeks 2 days ago

Here's the command :

grep '\(2\)[[:digit:]]\{\1\}' numbers

What I want is to match exactly 2 digits after the digit '2', 3 digits if I change the digit '2' to '3' in my expression, 4 digits if ...you got it

I'm using backreferencing here but when I execute this command I have the following output :

grep: invalid content of \{\}

How could one change my expression ?

first solution : As serg

I recently had trouble with some regex on the command-line, and found that for matching a backslash, different numbers of characters can be used. This number depends on the quoting used for the regex (none, single quotes, double quotes).

Using grep (or some other utility), is it possible to find all matches of a regular expression in a folder (searching the text of each file?) I want to find every match of the regular expression zenity within a specific folder, so that I can find the file that contains the string zenity.

Hi,

I'm on a Linux machine with a bash shell.