SED * operator Post: 302271163

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Top Forums Shell Programming and Scripting SED * operator Post 302271163 by matrixmadhan on Wednesday 24th of December 2008 03:45:12 AM

12-24-2008

Registered User

Quote:

Originally Posted by sinpeak

Thanks to all for the replies.

To matrixmadhan :

Going by your reply -

"It should match zero or more characters in the character class [a-z]
it will match 'a', 'b', 'c' and not the next space character <' '> so just that part is replaced by 'X'"

I tried :-

echo "a 123 abc" | sed 's/[a-z]*/X/'
echo "ab 123 abc" | sed 's/[a-z]*/X/'
echo "abc 123 abc" | sed 's/[a-z]*/X/'

all gave the same output as : X 123 abc

From your reply and the above result I understand - "*" will always start checking from the left in the input string. If it does not find a match , 'X' is replaced at the very beginning of the input string and the job is done.

But if it does find a match , it ends trying to find another match AND 'X' is kept in place of the matched token/characters.

Would request you to please confirm/correct the above.

Thanks

It will check from the start of the string ( <left of the string> ) and I hope this is what you meant, right?

Rest, you are right.

You need to remember this * means match zero or more characters.

There is going to be a definite replacement of zero or more matching characters.

matrixmadhan

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evmeventnamematchstr

EvmEventNameMatch(3)					     Library Functions Manual					      EvmEventNameMatch(3)

NAME

       EvmEventNameMatch(), EvmEventNameMatchStr() - match EVM event name

SYNOPSIS

   Library
       EVM Support Library

   Parameters
       pattern	     The  event name pattern sought.  The pattern may be any valid event name string.  It may include wildcard characters in place
		     of any component.

       event	     The event containing the event name to be compared against the pattern.

       match	     The result of the match. This operand is set to if the name matches the pattern, and to if it does not.

       candidate     A character string to be matched against the pattern

DESCRIPTION

       Because special matching rules apply when deciding whether a candidate event name matches a known name, the  EVM  name  matching  functions
       should  be  used  for matching purposes, rather than the C string comparison functions The EVM functions match an event name against a sup-
       plied pattern, ignoring any trailing appended components in the candidate name, and correctly matching wildcard characters.

       The function takes an event and an event name pattern as input, and returns an indication of  whether  the  event  contains  a  name  which
       matches the pattern in the match output argument.  The pattern may be any valid event name string, and may also include wildcard characters
       in place of any component.  A wildcard in the pattern matches zero or more name components.  A matches  exactly	one  component.   A  match
       occurs if the event name matches all components indicated by the pattern, even if the name has additional trailing elements.

       The function performs the same check as but takes a character string as the candidate event name, instead of extracting the candidate event
       name from a supplied event.

       Both functions set the match output argument to if the name matches the pattern, and to if it does not.

RETURN VALUE

       The operation completed without error.  The comparison was successful.  The value of the match operand indicates whether the  name  matches
       the pattern.

       One of the arguments to the function is invalid.
	      The supplied pattern contains invalid characters.

       The supplied event does not contain a name.

ERRORS

       The value of is not set.

SEE ALSO

   Routines
       memccpy(3C), strcat(3C).

   Event Management
       EVM(5).

   EVM Events
       EvmEvent(5).

															      EvmEventNameMatch(3)

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