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Full Discussion: grep fixed string with regex
Top Forums Shell Programming and Scripting grep fixed string with regex Post 302469759 by bakunin on Monday 8th of November 2010 04:43:25 AM
Old 11-08-2010
Quote:
Originally Posted by teresaejunior
Well, I need to make sure I grep only a word which may start with a lowercase letter or underline, the following characters may contain numbers and dashes aswell, and the last character can be a dollar sign.
It usually pays to simply re-read the definition you start with when constructing regexps. In this case:

1.) only a word
If we use the old IBM definition of a "word": A word is a sequence of non-blank characters, separated by blanks. ; we end up with something like:

Code:
grep '[<b><tab>]*[^<b><tab>][^<b><tab>][<b><tab>]*'

We search for an (optional) blank/tab character, followed by one or more non-blanks/non-tabs, followed by an optional tab/blank.

2.) which may start with a lowercase letter or underline,
Ok, we fine-tune our definition of the word:

Code:
grep '[<b><tab>]*[^_a-z][^<b><tab>][<b><tab>]*'

We search for an (optional) blank/tab character, followed by one underline or lowercase letter, more non-blanks/non-tabs, followed by an optional tab/blank.

3.) the following characters may contain numbers and dashes aswell,
more fine-tuning on what we mean by "word" here, i think it is self-explanatory now:

Code:
grep '[<b><tab>]*[^_a-z][-_a-z0-9][-_a-z0-9]*[<b><tab>]*'

4.) and the last character can be a dollar sign.
still more fine-tuning:

Code:
grep '[<b><tab>]*[^_a-z][-_a-z0-9][-_a-z0-9]*\$*[<b><tab>]*'

Probably we could drop the ending "[<b><tab>]*" now, because it might be superfluous - you will have to decide that by running the regexp against your data. Replace "<b>" and "<tab>" with literal blanks/tabs when you enter the code, i just used this to make them visible.

I hope this helps.

bakunin
 

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LEARN ABOUT HPUX

isprint

ctype(3C)																 ctype(3C)

NAME

       ctype:  isalnum(), isalpha(), isascii(), isblank(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(),
       isxdigit() - classify characters according to type

SYNOPSIS

DESCRIPTION

       These functions classify character-coded integer values according to the rules of the coded character set identified by the last successful
       call to (see setlocale(3C)).  Each function is a predicate returning nonzero for true, zero for false.

       If  has	not been called successfully, characters are classified according to the rules of the default ASCII 7-bit coded character set (see
       setlocale(3C)).

       is defined on all integer values; the other functions are defined for the range (EOF) through

RETURN VALUE

       The functions return nonzero under the following circumstances; zero otherwise:

	      c 		  is an alphanumeric (letters or digits).

	      c 		  is a letter.

	      c 		  is any ASCII character code between 0 and 0177, inclusive.

	      c 		  is a blank character; that is, a space or a tab.

	      c 		  is a control character (in ASCII: character codes less than 040 and the delete character(0177)).

	      c 		  is a decimal digit (in ASCII: characters [0-9]).

	      c 		  is a visible character (in ASCII: printing characters, excluding the space character(040)).

	      c 		  is a lowercase letter.

	      c 		  is a printing character.

	      c 		  is a punctuation character (in ASCII: any printing character except the space character(040), digits, letters).

	      c 		  is a character that creates whitespace in displayed text (in ASCII: space, tab, carriage return, newline, verti-
				  cal tab, and formfeed).

	      c 		  is an uppercase letter.

	      c 		  is a hexadecimal digit (in ASCII: characters [0-9], [A-F] or [a-f]).

       If the argument to any of these functions is outside the domain of the function, the result is undefined.

EXTERNAL INFLUENCES

   Environment Variables
       The category determines the classification of character type.

   International Code Set Support
       Single-byte character code sets are supported.

WARNINGS

       These  functions  are  supplied	both as library functions and as macros defined in the header.	Normally, the macro versions are used.	To
       obtain the library function, either use a to remove the macro definition or, if compiling in ANSI-C mode,  enclose  the	function  name	in
       parenthesis or take its address.  The following example uses the library functions for and

AUTHOR

       was developed by IBM, OSF, and HP.

SEE ALSO

       setlocale(3C), ascii(5), thread_safety(5).

STANDARDS CONFORMANCE

																	 ctype(3C)
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