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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	below)
	     is	a one-character	RE that	matches	itself.

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

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

	     b.	   ^ (caret or circumflex), which is special at	the  beginning
		   of an entire	RE (see	4.1 and	4.3 below), or when it immedi-
		   ately 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	entire
		   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 ex-
	     cept 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 cir-
	     cumflex (^), 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 consecutive charac-
	     ters; 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 charac-
	     ters.

       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-charac-
	     ter 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 exactly m occurrences; \{m,\} matches  at  least  m
	     occurrences;  \{m,n\} matches any number of occurrences between 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 concatenation
	     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 con-
	     sisting 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  fol-
	     low  a  character that is not a digit, underscore,	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 constrains 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  cur-
	  rent 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 con-
	  taining 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	minus)
	  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  preced-
	  ing  the  current line. (To maintain compatibility with earlier ver-
	  sions	of the editor, the character ^ in addresses is entirely	equiv-
	  alent	to -.) Moreover, trailing + and	- characters have a cumulative
	  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 re-
	     turn successive characters	of the regular expression.

       PEEKC This macro	returns	the next character (byte) in the  regular  ex-
	     pression.	Immediately  successive	 calls to  PEEKC should	return
	     the same character, which should also be the next	character  re-
	     turned 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 guaranteed to be the	last character
	     read by GETC. The return value of the macro UNGETC(c)  is	always
	     ignored.

       RETURN(ptr)
	     This  macro  is used on normal exit of the	compile() routine. The
	     value of the argument ptr is a pointer to the character after the
	     last character of the compiled regular 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 ERRORS below	for meanings).
	     This call should never return.

   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: 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 5.9			  2 Apr	1996			     regexp(5)

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

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