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Regular expression in grep command

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# 1  
Old 12-03-2015
Regular expression in grep command
Here is the content of a file:
Code:
abcdefgh
1234

When I do:
Code:
grep a?c <file>

I expect the output to show "abcdefgh". Its not happening. Any ideas?

"a?c" should mean either ac or c. This should mean the first line is a match. Yet its not happening. I have tried with -e option in grep, with and without single and double quotes and nothing worked.

Thanks
RC
Last edited by Scrutinizer; 12-03-2015 at 03:57 AM.. Reason: code tags
# 2  
Old 12-03-2015
Try
Code:
grep -E 'a?c' file

Default grep uses BRE (Basic Regular Expressions) and you need extended regular expressions (ERE) for this


--
The quotes are recommended to avoid a possible file name match using the Unix pattern a?c in the current directory, which could potentially influence the outcome of the grep
Last edited by Scrutinizer; 12-03-2015 at 04:08 AM..
This User Gave Thanks to Scrutinizer For This Post:
Rameshck
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