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regexp(5)	      Standards, Environments, and Macros	     regexp(5)

NAME
       regexp,	compile, step, advance - simple	regular	expression compile and
       match routines

SYNOPSIS
       #define INIT declarations
       #define GETC(void) getc code
       #define PEEKC(void) peekc code
       #define UNGETC(void) ungetc code
       #define RETURN(ptr) return code
       #define ERROR(val) error	code

       extern char *loc1, *loc2, *locs;

       #include	<regexp.h>

       char *compile(char *instring, char *expbuf,  const  char	 *endfug,  int
       eof);

       int step(const char *string, const char *expbuf);

       int advance(const char *string, const char *expbuf);

DESCRIPTION
       Regular	Expressions  (REs)  provide  a	mechanism  to  select specific
       strings from a set of character strings.	The Simple Regular Expressions
       described  below	differ from the	 Internationalized Regular Expressions
       described on the	 regex(5) manual page in the following ways:

	 o  only Basic Regular Expressions are supported

	 o  the	Internationalization  features--character  class,  equivalence
	    class, and multi-character collation--are not supported.

       The functions step(), advance(),	and compile() are general purpose reg-
       ular expression matching	routines to be used in programs	 that  perform
       regular	expression  matching. These functions are defined by the <reg-
       exp.h> header.

       The functions step() and	advance() do pattern matching given a  charac-
       ter string and a	compiled regular expression as input.

       The  function  compile()	takes as input a regular expression as defined
       below and produces a compiled expression	that can be used  with	step()
       or advance().

   Basic Regular Expressions
       A  regular expression specifies a set of	character strings. A member of
       this set	of strings is said to be matched by  the  regular  expression.
       Some characters have special meaning when used in a regular expression;
       other characters	stand for themselves.

       The following one-character REs match a single character:

       1.1	An ordinary character (	not one	of those discussed in 1.2  be-
		low) is	a one-character	RE that	matches	itself.

       1.2	A  backslash  (\)  followed by any special character is	a one-
		character RE that matches the special  character  itself.  The
		special	characters are:

		a.	 .,  *,	 [,  and  \  (period,  asterisk,  left	square
			 bracket, and backslash, respectively),	which are  al-
			 ways  special,	 except	when they appear within	square
			 brackets ([]; see 1.4 below).

		b.	 ^ (caret or circumflex), which	is special at the  be-
			 ginning  of  an entire	RE (see	4.1 and	4.3 below), or
			 when it immediately follows the left  of  a  pair  of
			 square	brackets ([]) (see 1.4 below).

		c.	 $  (dollar  sign),  which is special at the end of an
			 entire	RE (see	4.2 below).

		d.	 The character used to bound (that is, delimit)	an en-
			 tire  RE,  which is special for that RE (for example,
			 see how slash (/) is used in the g command, below.)

       1.3	A period (.) is	a one-character	RE that	matches	any  character
		except new-line.

       1.4	A  non-empty  string of	characters enclosed in square brackets
		([]) is	a one-character	RE that	matches	any one	 character  in
		that string. If, however, the first character of the string is
		a circumflex (^), the one-character RE matches	any  character
		except	new-line  and  the remaining characters	in the string.
		The ^ has this special meaning only if it occurs first in  the
		string.	 The minus (-) may be used to indicate a range of con-
		secutive characters;  for  example,  [0-9]  is	equivalent  to
		[0123456789].  The  -  loses this special meaning if it	occurs
		first (after an	initial	^, if any) or last in the string.  The
		right square bracket (]) does not terminate such a string when
		it is the first	character within it (after an  initial	^,  if
		any);  for  example,  []a-f]  matches  either  a  right	square
		bracket	(]) or one of the ASCII	letters	a through f inclusive.
		The four characters listed in 1.2.a above stand	for themselves
		within such a string of	characters.

       The following rules may be used to  construct  REs  from	 one-character
       REs:

       2.1	       A  one-character	 RE  is	a RE that matches whatever the
		       one-character RE	matches.

       2.2	       A one-character RE followed by an asterisk (*) is a  RE
		       that matches 0 or more occurrences of the one-character
		       RE. If there is any choice, the longest leftmost	string
		       that permits a match is chosen.

       2.3	       A  one-character	 RE  followed  by  \{m\},  \{m,\},  or
		       \{m,n\} is a RE that matches a range of occurrences  of
		       the  one-character  RE.	The  values of m and n must be
		       non-negative integers less than 256; \{m\} matches  ex-
		       actly  m	 occurrences; \{m,\} matches at	least m	occur-
		       rences; \{m,n\} matches any number of  occurrences  be-
		       tween  m	and n inclusive. Whenever a choice exists, the
		       RE matches as many occurrences as possible.

       2.4	       The concatenation of REs	is a RE	that matches the  con-
		       catenation  of the strings matched by each component of
		       the RE.

       2.5	       A RE enclosed between the character sequences \(	and \)
		       is a RE that matches whatever the unadorned RE matches.

       2.6	       The expression \n matches the same string of characters
		       as was matched by an expression enclosed	between	\( and
		       \)  earlier in the same RE. Here	n is a digit; the sub-
		       expression specified is that beginning  with  the  n-th
		       occurrence  of  \( counting from	the left. For example,
		       the expression ^\(.*\)\1$ matches a line	consisting  of
		       two repeated appearances	of the same string.

       An RE may be constrained	to match words.

       3.1	       \<  constrains  a RE to match the beginning of a	string
		       or to follow a character	that is	not  a	digit,	under-
		       score,  or  letter. The first character matching	the RE
		       must be a digit,	underscore, or letter.

       3.2	       \> constrains a RE to match the end of a	string	or  to
		       precede a character that	is not a digit,	underscore, or
		       letter.

       An entire RE may	be constrained to match	only an	initial	segment	or fi-
       nal segment of a	line (or both).

       4.1	       A  circumflex (^) at the	beginning of an	entire RE con-
		       strains that RE to match	an initial segment of a	line.

       4.2	       A dollar	sign ($) at the	end of an entire RE constrains
		       that RE to match	a final	segment	of a line.

       4.3	       The  construction  ^entire RE$ constrains the entire RE
		       to match	the entire line.

       The null	RE (for	example, //) is	equivalent to the last RE encountered.

   Addressing with REs
       Addresses are constructed as follows:

       1.  The character "." addresses the current line.

       2.  The character "$" addresses the last	line of	the buffer.

       3.  A decimal number n addresses	the n-th line of the buffer.

       4.  'x addresses	the line marked	with the mark name character x,	 which
	   must	be an ASCII lower-case letter (a-z). Lines are marked with the
	   k command described below.

       5.  A RE	enclosed by slashes (/)	addresses  the	first  line  found  by
	   searching  forward  from the	line following the current line	toward
	   the end of the buffer and stopping at the first line	 containing  a
	   string  matching  the  RE. If necessary, the	search wraps around to
	   the beginning of the	buffer and continues up	to and	including  the
	   current line, so that the entire buffer is searched.

       6.  A  RE enclosed in question marks (?)	addresses the first line found
	   by searching	backward from the line preceding the current line  to-
	   ward	 the  beginning	 of  the buffer	and stopping at	the first line
	   containing a	string matching	the RE.	If necessary, the search wraps
	   around  to  the end of the buffer and continues up to and including
	   the current line.

       7.  An address followed by a plus sign (+) or a minus sign (-) followed
	   by  a  decimal number specifies that	address	plus (respectively mi-
	   nus)	the indicated number of	lines. A shorthand for .+5 is .5.

       8.  If an address begins	with + or -, the addition  or  subtraction  is
	   taken  with	respect	to the current line; for example, -5 is	under-
	   stood to mean .-5.

       9.  If an address ends with + or	-, then	1 is added  to	or  subtracted
	   from	 the  address, respectively. As	a consequence of this rule and
	   of Rule 8, immediately above, the address - refers to the line pre-
	   ceding  the	current	line.  (To maintain compatibility with earlier
	   versions of the editor, the character ^ in  addresses  is  entirely
	   equivalent  to -.) Moreover,	trailing + and - characters have a cu-
	   mulative effect, so -- refers to the	current	line less 2.

       10. For convenience, a comma (,)	stands for the address pair 1,$, while
	   a semicolon (;) stands for the pair .,$.

   Characters With Special Meaning
       Characters  that	 have  special	meaning	except when they appear	within
       square brackets ([]) or are preceded by \ are:  ., *, [,	\. Other  spe-
       cial characters,	such as	$ have special meaning in more restricted con-
       texts.

       The character ^ at the beginning	of an expression permits a  successful
       match  only immediately after a newline,	and the	character $ at the end
       of an expression	requires a trailing newline.

       Two characters have special meaning only	when used within square	brack-
       ets.  The  character  - denotes a range,	[c-c], unless it is just after
       the open	bracket	or before the closing bracket, [-c] or [c-]  in	 which
       case  it	has no special meaning.	When used within brackets, the charac-
       ter ^ has the meaning complement	of if it immediately follows the  open
       bracket	(example: [^c]); elsewhere between brackets (example: [c^]) it
       stands for the ordinary character ^.

       The special meaning of the \ operator can be escaped only by  preceding
       it with another \, for example \\.

   Macros
       Programs	 must  have the	following five macros declared before the #in-
       clude <regexp.h>	statement. These macros	are used by the	compile() rou-
       tine. The macros	GETC, PEEKC, and UNGETC	operate	on the regular expres-
       sion given as input to compile().

       GETC	       This macro returns the  value  of  the  next  character
		       (byte)  in  the	regular	expression pattern. Successive
		       calls to	 GETC should return successive	characters  of
		       the regular expression.

       PEEKC	       This  macro  returns  the  next character (byte)	in the
		       regular expression.  Immediately	 successive  calls  to
		       PEEKC  should  return  the same character, which	should
		       also be the next	character returned by GETC.

       UNGETC	       This macro causes the argument c	to be returned by  the
		       next call to GETC and PEEKC. No more than one character
		       of pushback is ever needed and this character is	 guar-
		       anteed  to  be the last character read by GETC. The re-
		       turn value of the macro UNGETC(c) is always ignored.

       RETURN(ptr)     This macro is used on normal exit of the	compile() rou-
		       tine. The value of the argument ptr is a	pointer	to the
		       character after the last	character of the compiled reg-
		       ular  expression. This is useful	to programs which have
		       memory allocation to manage.

       ERROR(val)      This macro is the abnormal return  from	the  compile()
		       routine.	 The  argument val is an error number (see ER-
		       RORS below for meanings). This call  should  never  re-
		       turn.

   compile()
       The syntax of the compile() routine is as follows:

	      compile(instring,	expbuf,	endbuf,	eof)

       The  first  parameter,  instring,  is never used	explicitly by the com-
       pile() routine but is useful for	 programs  that	 pass  down  different
       pointers	to input characters. It	is sometimes used in the INIT declara-
       tion (see below). Programs which	call functions to input	characters  or
       have characters in an external array can	pass down a value of (char *)0
       for this	parameter.

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

       The  parameter  endbuf  is  one more than the highest address where the
       compiled	regular	expression may be placed. If the  compiled  expression
       cannot fit in (endbuf-expbuf) bytes, a call to ERROR(50)	is made.

       The  parameter  eof is the character which marks	the end	of the regular
       expression. This	character is usually a /.

       Each program that includes the <regexp.h> header	file must have a  #de-
       fine statement for INIT.	It is used for dependent declarations and ini-
       tializations. Most often	it is used to set a register variable to point
       to  the beginning of the	regular	expression so that this	register vari-
       able can	be used	in the declarations for	GETC, PEEKC, and UNGETC.  Oth-
       erwise  it can be used to declare external variables that might be used
       by GETC,	PEEKC and UNGETC. (See EXAMPLES	below.)

   step(), advance()
       The first parameter to the step() and advance() functions 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	 which
       was obtained by a call to the function compile().

       The  function  step()  returns  non-zero	 if  some  substring of	string
       matches the regular expression in expbuf	and  0 if there	is  no	match.
       If  there is a match, two external character pointers are set as	a side
       effect to the call to step(). The variable loc1	points	to  the	 first
       character that matched the regular expression; the variable loc2	points
       to the character	after the last character that matches the regular  ex-
       pression.  Thus	if  the	 regular  expression  matches the entire input
       string, loc1 will point to the first character of string	and loc2  will
       point to	the null at the	end of string.

       The  function  advance()	 returns  non-zero if the initial substring of
       string matches the regular expression in	expbuf.	If there is  a	match,
       an external character pointer, loc2, is set as a	side effect. The vari-
       able loc2 points	to the next character in string	after the last charac-
       ter that	matched.

       When  advance() encounters a * or \{ \} sequence	in the regular expres-
       sion, it	will advance its pointer to the	string to be matched as	far as
       possible	 and  will recursively call itself trying to match the rest of
       the string to the rest of the regular expression. As long as  there  is
       no  match,  advance()  will  back  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 locs is equal to	the point in the string	at sometime during the
       backing up process, advance() will break	out of the loop	that backs  up
       and will	return zero.

       The external variables circf, sed, and nbra are reserved.

EXAMPLES
       Example 1: Using	Regular	Expression Macros and Calls

       The  following  is  an example of how the regular expression macros and
       calls might be defined by an application	program:

       #define INIT	  register char	*sp = instring;
       #define GETC()	  (*sp++)
       #define PEEKC()	  (*sp)
       #define UNGETC(c)  (--sp)
       #define RETURN(c)  return;
       #define ERROR(c)	  regerr()

       #include	<regexp.h>
	. . .
	     (void) compile(*argv, expbuf, &expbuf[ESIZE],'\0');
	. . .
	     if	(step(linebuf, expbuf))
			       succeed;

DIAGNOSTICS
       The function compile() uses the macro RETURN on success and  the	 macro
       ERROR on	failure	(see above). The functions step() and advance()	return
       non-zero	on a successful	match and zero if there	is no  match.	Errors
       are:

       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.

SEE ALSO
       regex(5)

SunOS 5.10			  20 May 2002			     regexp(5)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | DIAGNOSTICS | SEE ALSO

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