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NAME    [Toc]    [Back]

       regcomp, regexec, regerror, regfree - POSIX regex functions

SYNOPSIS    [Toc]    [Back]

       #include <sys/types.h>
       #include <regex.h>

       int regcomp(regex_t *preg, const char *regex, int cflags);
       int regexec(const  regex_t  *preg,  const  char *string, size_t nmatch,
		   regmatch_t pmatch[], int eflags);
       size_t regerror(int errcode, const regex_t *preg, char *errbuf,	size_t
       void regfree(regex_t *preg);


       regcomp	is  used  to  compile a regular expression into a form that is
       suitable for subsequent regexec searches.

       regcomp is supplied with preg, a pointer to a  pattern  buffer  storage
       area;  regex, a pointer to the null-terminated string and cflags, flags
       used to determine the type of compilation.

       All regular expression searching must be done via  a  compiled  pattern
       buffer, thus regexec must always be supplied with the address of a reg-
       comp initialised pattern buffer.

       cflags may be the bitwise-or of one or more of the following:

       REG_EXTENDED    [Toc]    [Back]
	      Use POSIX Extended Regular Expression syntax  when  interpreting
	      regex.   If  not	set,  POSIX Basic Regular Expression syntax is

       REG_ICASE    [Toc]    [Back]
	      Do not differentiate case.  Subsequent  regexec  searches  using
	      this pattern buffer will be case insensitive.

       REG_NOSUB    [Toc]    [Back]
	      Support  for  substring  addressing  of matches is not required.
	      The nmatch and pmatch parameters to regexec are ignored  if  the
	      pattern buffer supplied was compiled with this flag set.

       REG_NEWLINE    [Toc]    [Back]
	      Match-any-character operators don't match a newline.

	      A  non-matching list ([^...])  not containing a newline does not
	      match a newline.

	      Match-beginning-of-line operator (^) matches  the  empty	string
	      immediately  after  a newline, regardless of whether eflags, the
	      execution flags of regexec, contains REG_NOTBOL.

	      Match-end-of-line operator ($) matches the empty string  immediately
  before  a	newline, regardless of whether eflags contains


       regexec is used to match a null-terminated string against  the  precompiled
  pattern  buffer,	preg.	nmatch	and pmatch are used to provide
       information regarding the location of any matches.  eflags may  be  the
       bitwise-or  of  one  or	both  of REG_NOTBOL and REG_NOTEOL which cause
       changes in matching behaviour described below.

       REG_NOTBOL    [Toc]    [Back]
	      The match-beginning-of-line operator always fails to match  (but
	      see  the	compilation  flag  REG_NEWLINE above) This flag may be
	      used when different portions of a string are passed  to  regexec
	      and the beginning of the string should not be interpreted as the
	      beginning of the line.

       REG_NOTEOL    [Toc]    [Back]
	      The match-end-of-line operator always fails to  match  (but  see
	      the compilation flag REG_NEWLINE above)

   BYTE OFFSETS    [Toc]    [Back]
       Unless  REG_NOSUB was set for the compilation of the pattern buffer, it
       is possible to obtain substring match addressing  information.	pmatch
       must be dimensioned to have at least nmatch elements.  These are filled
       in by regexec with substring match  addresses.	Any  unused  structure
       elements will contain the value -1.

       The  regmatch_t	structure  which  is  the type of pmatch is defined in

	      typedef struct
		regoff_t rm_so;
		regoff_t rm_eo;
	      } regmatch_t;

       Each rm_so element that is not -1 indicates the	start  offset  of  the
       next  largest  substring  match	within the string.  The relative rm_eo
       element indicates the end offset of the match.


       regerror is used to turn the error codes that can be returned  by  both
       regcomp and regexec into error message strings.

       regerror is passed the error code, errcode, the pattern buffer, preg, a
       pointer to a character string buffer,  errbuf,  and  the  size  of  the
       string buffer, errbuf_size.  It returns the size of the errbuf required
       to contain the null-terminated error message string.   If  both	errbuf
       and  errbuf_size  are  non-zero,  errbuf  is  filled  in with the first
       errbuf_size - 1 characters of the error message and a terminating null.


       Supplying regfree with a precompiled pattern buffer, preg will free the
       memory allocated to the pattern buffer by the compiling	process,  reg-

RETURN VALUE    [Toc]    [Back]

       regcomp	returns zero for a successful compilation or an error code for

       regexec returns zero for a successful match or REG_NOMATCH for failure.

ERRORS    [Toc]    [Back]

       The following errors can be returned by regcomp:

       REG_BADRPT    [Toc]    [Back]
	      Invalid  use  of	repetition  operators such as using `*' as the
	      first character.

       REG_BADBR    [Toc]    [Back]
	      Invalid use of back reference operator.

       REG_EBRACE    [Toc]    [Back]
	      Un-matched brace interval operators.

       REG_EBRACK    [Toc]    [Back]
	      Un-matched bracket list operators.

       REG_ERANGE    [Toc]    [Back]
	      Invalid use of the range operator, eg. the ending point  of  the
	      range occurs prior to the starting point.

       REG_ECTYPE    [Toc]    [Back]
	      Unknown character class name.

       REG_ECOLLATE    [Toc]    [Back]
	      Invalid collating element.

       REG_EPAREN    [Toc]    [Back]
	      Un-matched parenthesis group operators.

       REG_ESUBREG    [Toc]    [Back]
	      Invalid back reference to a subexpression.

       REG_EEND    [Toc]    [Back]
	      Non specific error.  This is not defined by POSIX.2.

       REG_EESCAPE    [Toc]    [Back]
	      Trailing backslash.

       REG_BADPAT    [Toc]    [Back]
	      Invalid use of pattern operators such as group or list.

       REG_ESIZE    [Toc]    [Back]
	      Compiled	regular  expression  requires  a pattern buffer larger
	      than 64Kb.  This is not defined by POSIX.2.

       REG_ESPACE    [Toc]    [Back]
	      The regex routines ran out of memory.

CONFORMING TO    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

       regex(7), GNU regex manual

GNU				  1998-05-08			    REGCOMP(3)
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