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Full Discussion: Regular expression help
Top Forums UNIX for Dummies Questions & Answers Regular expression help Post 302757959 by radoulov on Friday 18th of January 2013 08:49:26 AM
Old 01-18-2013
Quote:
Originally Posted by frodo61
Thank you for explaining. If my shell doesnt support regular expressions why does some of the regular expression work in my code?
Give an example, please. They were most probably valid as shell patterns too.

Quote:
I will try usng the grep example instead but how would I make a single dot optionally instead of mandatory, would it be \? after the dot?
To match zero or one . use .?.

EDIT: Correct, in a basic regular expression you should use \?.

Last edited by radoulov; 01-18-2013 at 10:29 AM..
 

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REGEX(3)						     Library Functions Manual							  REGEX(3)

NAME
re_comp, re_exec - regular expression handler SYNOPSIS
char *re_comp(s) char *s; re_exec(s) char *s; DESCRIPTION
Re_comp compiles a string into an internal form suitable for pattern matching. Re_exec checks the argument string against the last string passed to re_comp. Re_comp returns 0 if the string s was compiled successfully; otherwise a string containing an error message is returned. If re_comp is passed 0 or a null string, it returns without changing the currently compiled regular expression. Re_exec returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled regular expression, and -1 if the compiled regular expression was invalid (indicating an internal error). The strings passed to both re_comp and re_exec may have trailing or embedded newline characters; they are terminated by nulls. The regular expressions recognized are described in the manual entry for ed(1), given the above difference. SEE ALSO
ed(1), ex(1), egrep(1), fgrep(1), grep(1) DIAGNOSTICS
Re_exec returns -1 for an internal error. Re_comp returns one of the following strings if an error occurs: No previous regular expression, Regular expression too long, unmatched (, missing ], too many () pairs, unmatched ). 3rd Berkeley Distribution May 15, 1985 REGEX(3)
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