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regexp question, this regexp doesn't seem to do what I expect it to, why?

ericode	14 Oct, 2007 - 09:36 PM Post #1
D.I.C Head Joined: 9 Dec, 2006 Posts: 89 Dream Kudos: 75 My Contributions	I have a file named bintxt.txt with the binary string representations of the numbers 0 through 600, each on a separate line. When I run the following command (in Linux), I get no results grep '^1(01)0$' bintxt.txt And fittingly, when I run the following command, I get all the lines in the file grep --invert-match '^1(01)0$' bintxt.txt I thought that this regular expression would match lines consisting of any number of 1's followed by any number of 01s followed by any number of 0's (for example, 0,00, 1, 101010, etc would match) Could someone explain why the regular expression is not working as I thought it would?
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ericode	RE: Regexp Question 16 Oct, 2007 - 09:43 AM Post #2
D.I.C Head Joined: 9 Dec, 2006 Posts: 89 Dream Kudos: 75 My Contributions	QUOTE(ericode @ 14 Oct, 2007 - 10:36 PM) I have a file named bintxt.txt with the binary string representations of the numbers 0 through 600, each on a separate line. When I run the following command (in Linux), I get no results grep '^1(01)0$' bintxt.txt And fittingly, when I run the following command, I get all the lines in the file grep --invert-match '^1(01)0$' bintxt.txt I thought that this regular expression would match lines consisting of any number of 1's followed by any number of 01s followed by any number of 0's (for example, 0,00, 1, 101010, etc would match) Could someone explain why the regular expression is not working as I thought it would? Found the answer to my question: the parentheses need to be escaped as so: grep '^1\(01\)0*$' bintxt.txt
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