regexp(3X)																regexp(3X)

NAME

       compile(), step(), advance() - regular expression compile and match routines

SYNOPSIS

   Remarks
       Features  documented  in  this  manual  entry  are  obsolescent and may be removed in a future HP-UX release.  Use of regcomp(3C) functions
       instead is recommended.

DESCRIPTION

       These functions are general-purpose regular expression matching routines to be used in programs that perform Basic Regular Expression  (see
       regexp(5)) matching.  These functions are defined in

       The  functions  and do pattern matching given a character string and a compiled regular expression as input.  takes a Basic Regular Expres-
       sion as input and produces a compiled expression that can be used with and

       The interface to this file is unpleasantly complex.  Programs that include this file must have the following five  macros  declared  before
       the statement.  These macros are used by the routine.

       Return the value of the next byte
		      in the regular expression pattern.  Successive calls to should return successive bytes of the regular expression.

       Return the next byte in the regular
		      expression.  Successive calls to should return the same byte (which should also be the next byte returned by

       Cause the argument
		      c  to  be returned by the next call to (and No more than one byte of pushback is ever needed, and this byte is guaranteed to
		      be the last byte read by The value of the macro is always ignored.

       This macro is used on normal exit of the
		      routine.	The value of the argument pointer is a pointer to the character after the last character of the  compiled  regular
		      expression.  This is useful to programs that must manage memory allocation.

       This is the abnormal return from the
		      routine.	The argument val is an error number (see table below for meanings).  This call should never return.
			   11	   Range endpoint too large.
			   16	   Bad number.
			   25	   ``digit'' out of range.
			   36	   Illegal or missing delimiter.
			   41	   No remembered search string.
			   42	   imbalance.
			   43	   Too many
			   44	   More than 2 numbers given in
			   45	   expected after
			   46	   First number exceeds second in
			   49	   imbalance.
			   50	   Regular expression overflow.

       The syntax of the routine is as follows:

       The first parameter instring is never used explicitly by the routine, but is useful for programs that pass down different pointers to input
       characters.  It is sometimes used in the declaration (see below).  Programs that call functions to input characters or have  characters	in
       an external array can pass down a value of for this parameter.

       The next parameter expbuf is a character pointer.  It points to the location where the compiled regular expression will be placed.

       The  parameter endbuf is one more than the highest address where the compiled regular expression can be placed.	If the compiled expression
       cannot fit in (endbuf-expbuf) bytes, a call to is made.

       The parameter eof is the character which marks the end of the regular expression.  For example, in ed(1), this character is usually a

       Each program that includes this file must have a statement for This definition is placed right after the declaration for the  function  and
       the  opening  curly  brace  It is used for dependent declarations and initializations.  Most often it is used to set a register variable to
       point to the beginning of the regular expression so that this register variable can be used in the declarations for and Otherwise it can be
       used to declare external variables that might be used by and See the example below of the declarations taken from grep(1).

       also performs actual regular expression matching in this file.  The call to step is as follows:

       The first parameter to is a pointer to a string of characters to be checked for a match.  This string should be null-terminated.

       The second parameter expbuf is the compiled regular expression that was obtained by a call to

       returns	non-zero  if  the given string matches the regular expression, and zero if the expressions do not match.  If there is a match, two
       external character pointers are set as a side effect to the call to The variable set in is This is a pointer to the  first  character  that
       matched	the  regular  expression.  The variable which is set by the function points to the character after the last character that matches
       the regular expression.	Thus, if the regular expression matches the entire line, points to the first character of string and points to the
       null at the end of string.

       uses  the  external variable which is set by if the regular expression begins with If this is set, tries to match the regular expression to
       the beginning of the string only.  If more than one regular expression is to be compiled before the first is executed, the value  of  circf
       should be saved for each compiled expression and circf should be set to that saved value before each call to

       is  called  from  with  the  same arguments as The purpose of is to step through the string argument and call until returns non-zero, which
       indicates a match, or until the end of string is reached.  To constrain string to beginning-of-line in all cases, need not be called;  sim-
       ply call

       When  encounters a or sequence in the regular expression, it advances its pointer to the string to be matched as far as possible and recur-
       sively calls itself, trying to match the rest of the string to the rest of the regular expression.  As long as there is no  match,  advance
       backs up along the string until it finds a match or reaches the point in the string that initially matched the or It is sometimes desirable
       to stop this backing up before the initial point in the string is reached.  If the external character pointer is equal to the point in  the
       string  at sometime during the backing up process, breaks out of the loop that backs up and returns zero.  This is used by ed(1) and sed(1)
       for substitutions done globally (not just the first occurrence, but the whole line) so, for example, expressions such as do not	loop  for-
       ever.

       The additional external variables and are used for special purposes.

EXTERNAL INFLUENCES

   Locale
       The category determines the collating sequence used in compiling and executing regular expressions.

       The  category  determines  the interpretation of text as single and/or multi-byte characters, and the characters matched by character class
       expressions in regular expressions.

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

EXAMPLES

       The following is an example of how the regular expression macros and calls look from grep(1):

		   ...
		   ...

SEE ALSO

       grep(1), regcomp(3C), setlocale(3C), regexp(5).

STANDARDS CONFORMANCE

																	regexp(3X)