regex man page on DigitalUNIX

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regcmp(3)							     regcmp(3)

       regcmp, regex - Compile and execute regular expression

       #include <libgen.h>

       char *regcmp(
	       const char *string1,
	       ... /*,
	       (char *)0 */ ); char *regex(
	       const char *re,
	       const char *subject,
	       ...  );

       Standard C Library (libc)

       Interfaces  documented on this reference page conform to industry stan‐
       dards as follows:

       regcmp(), regex():  XPG4-UNIX

       Refer to the standards(5) reference page	 for  more  information	 about
       industry standards and associated tags.

       Points  to  the string that is to be matched or converted.  Points to a
       compiled regular expression string.  Points to the string that is to be
       matched against re.

       The  regcmp()  function compiles a regular expression consisting of the
       concatenated arguments and returns a pointer to the compiled form.  The
       end  of arguments is indicated by a null pointer. The malloc() function
       is used to create space for the compiled form. It is the responsibility
       of  the	process	 to  free  unneeded space so allocated. A null pointer
       returned from regcmp() indicates an invalid argument.

       The regex() function executes a compiled pattern	 against  the  subject
       string.	Additional  arguments  of  type char must be passed to receive
       matched subexpressions back. A global character pointer, __loc1, points
       to the first matched character in the subject string.

       The  regcmp()  and regex() functions support the simple regular expres‐
       sions which are defined in the grep(1) reference page, but  the	syntax
       and  semantics are slightly different. The following are the valid sym‐
       bols and their associated meanings: The left and right bracket,	aster‐
       isk, period, and circumflex symbols retain their meanings as defined in
       the grep(1) reference page.  A dollar  sign  matches  the  end  of  the
       string; \n matches a new line.  Used within brackets, the hyphen signi‐
       fies an ASCII character range.  For  example  [a-z]  is	equivalent  to
       [].  The  - (hyphen) can represent itself only if used as the
       first or last character.	 For example, the character  class  expression
       []-]  matches the characters ] (right bracket) and - (hyphen).  A regu‐
       lar expression followed by a + (plus sign) means one or more times. For
       example,	 [0-9]+ is equivalent to [0-9][0-9]*.  Integer values enclosed
       in {} braces indicate the number of times the preceding regular expres‐
       sion  can be applied. The value m is the minimum number and u is a num‐
       ber, less than 256, which is the maximum. The syntax {m} indicates  the
       exact number of times the regular expression can be applied. The syntax
       {m,} is analogous to {m,infinity}. The + (plus sign) and	 *  (asterisk)
       operations are equivalent to {1,} and {0,}, respectively.  The value of
       the enclosed regular expression is returned.  The value	is  stored  in
       the  (n+1)th argument following the subject argument.  A maximum of ten
       enclosed regular expressions are allowed. The  regex()  function	 makes
       its assignments unconditionally.	 Parentheses are used for grouping. An
       operator, such as *, +, or {}, can work on a single character or a reg‐
       ular expression enclosed in parentheses. For example, (a*(cb+)*)$0.

       Since  all  of  the  symbols defined above are special characters, they
       must be escaped to be used as themselves.

       The regcmp() and regex() interfaces are scheduled to be withdrawn  from
       a future version of the X/Open CAE Specification.

       These interfaces are obsolete; they are guaranteed to function properly
       only in the C/POSIX locale and so should be avoided. Use the POSIX reg‐
       comp() interface instead of regcmp() and regex().

       Upon  successful completion, the regcmp() function returns a pointer to
       the compiled regular expression. Otherwise, a null pointer is  returned
       and errno may be set to indicate the error.

       Upon  successful	 completion, the regex() function returns a pointer to
       the next unmatched character in the subject string. Otherwise,  a  null
       pointer is returned.

       Commands: grep(1)

       Functions: malloc(3), regcomp(3)

       Standards: standards(5)


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