Need help with Regular Expressions and nested loops Post: 302525247

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Top Forums Shell Programming and Scripting Need help with Regular Expressions and nested loops Post 302525247 by zaxxon on Thursday 26th of May 2011 07:00:03 AM

05-26-2011

Registered User

Tools like grep, sed, awk etc. use reg exp. If you want to get familiar with reg exps, maybe try to start working with those 3 tools. For grep there is grep -E or egrep, which gives access to a broader range of regular expressions than a simple grep.

For reg exps checkout this:
Regular Expressions

For the use of regular expressions in a shell (test in double brackets) I just found this in the bash man page:

Code:

              An additional binary operator, =~, is available, with the same precedence as == and !=.  When it is used, the string to the right of  the
              operator  is  considered  an  extended  regular expression and matched accordingly (as in regex(3)).  The return value is 0 if the string
              matches the pattern, and 1 otherwise.  If the regular expression is syntactically incorrect, the conditional expression's return value is ...

Can also try playing around with this.

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LEARN ABOUT ULTRIX

regex

regex(3)						     Library Functions Manual							  regex(3)

Name
       re_comp, re_exec - regular expression handler

Syntax
       char *re_comp(s)
       char *s;

       re_exec(s)
       char *s;

Description
       The  subroutine	compiles  a string into an internal form suitable for pattern matching.  The subroutine checks the argument string against
       the last string passed to

       The subroutine returns 0 if the string s was compiled successfully; otherwise a string containing an  error  message  is  returned.  If	is
       passed 0 or a null string, it returns without changing the currently compiled regular expression.

       The  subroutine 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 and may have trailing or embedded newline characters; they are terminated by	nulls.	 The  regular  expressions
       recognized are described in the manual entry for given the above difference.

Diagnostics
       The subroutine returns -1 for an internal error.

       The subroutine returns one of the following strings if an error occurs:

       No previous regular expression
       Regular expression too long
       unmatched (
       missing ]
       too many () pairs
       unmatched )

See Also
       ed(1), ex(1), egrep(1), fgrep(1), grep(1)

																	  regex(3)