Regular Exprasions


 
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# 1  
Regular Exprasions

HI i am new to Unix&LInux world my question is
what dose the question mark ins this command mean
Code:
find . –type d –name “?d*” –print

i tried to to run it without it did not notice any change.
Thx.

Last edited by Scrutinizer; 03-27-2013 at 03:23 PM..
# 2  
That's a wildcard, not a regular expression ("?" stands for a single character).

Some implementations of "find" support "regex" and "iregex" flags.
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# 3  
Any single character.

See Shell Command Language (and note that find uses pattern matching notation, not regular expressions as such).
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# 4  
In case the previous comments were too cryptic, the command:
Code:
find . –type d –name "?d*" –print

will look for files in or under the current directory (.) of type directory (-type d) with a name that is any single character followed by the letter d followed by zero or more other characters (-name "?d*"and prints the pathnames of any files that match these criteria (-print).

Note that I used "?d*", not ?d*. Although opening- and closing-double-quote characters may be nicer visually when typing text, plain double-quote characters are required when passing arguments to the shell (unless you're actually looking for files with names containing the opening- and closing-double-quote characters).

Also note that the -print primary is not needed in this find command because it just specifies the default behavior in this case.
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