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RedHat 9 (Linux i386) - man page for regex (redhat section 3)

REGCOMP(3)			    Linux Programmer's Manual			       REGCOMP(3)

NAME
       regcomp, regexec, regerror, regfree - POSIX regex functions

SYNOPSIS
       #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 errbuf_size);
       void regfree(regex_t *preg);

POSIX REGEX COMPILING
       regcomp is used to compile a regular expression into a form that is  suitable  for  subse-
       quent 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 com-
       pilation.

       All  regular expression searching must be done via a compiled pattern buffer, thus regexec
       must always be supplied with the address of a regcomp initialized pattern buffer.

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

       REG_EXTENDED
	      Use POSIX Extended Regular Expression syntax when interpreting regex.  If not  set,
	      POSIX Basic Regular Expression syntax is used.

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

       REG_NOSUB
	      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
	      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  new-
	      line, regardless of whether eflags contains REG_NOTEOL.

POSIX REGEX MATCHING
       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
	      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
	      The  match-end-of-line operator always fails to match (but see the compilation flag
	      REG_NEWLINE above)

   BYTE OFFSETS
       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 regex.h.

	      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.

POSIX ERROR REPORTING
       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 char-
       acter  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.

POSIX PATTERN BUFFER FREEING
       Supplying regfree with a precompiled pattern buffer, preg will free the	memory	allocated
       to the pattern buffer by the compiling process, regcomp.

RETURN VALUE
       regcomp returns zero for a successful compilation or an error code for failure.

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

ERRORS
       The following errors can be returned by regcomp:

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

       REG_BADBR
	      Invalid use of back reference operator.

       REG_EBRACE
	      Un-matched brace interval operators.

       REG_EBRACK
	      Un-matched bracket list operators.

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

       REG_ECTYPE
	      Unknown character class name.

       REG_ECOLLATE
	      Invalid collating element.

       REG_EPAREN
	      Un-matched parenthesis group operators.

       REG_ESUBREG
	      Invalid back reference to a subexpression.

       REG_EEND
	      Non specific error.  This is not defined by POSIX.2.

       REG_EESCAPE
	      Trailing backslash.

       REG_BADPAT
	      Invalid use of pattern operators such as group or list.

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

       REG_ESPACE
	      The regex routines ran out of memory.

CONFORMING TO
       POSIX.2

SEE ALSO
       regex(7), GNU regex manual

GNU					    1998-05-08				       REGCOMP(3)


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