REGEXP(2)							System Calls Manual							 REGEXP(2)

NAME

       regcomp, regcomplit, regcompnl, regexec, regsub, rregexec, rregsub, regerror - regular expression

SYNOPSIS

       #include <u.h>
       #include <libc.h>
       #include <regexp.h>

       Reprog  *regcomp(char *exp)

       Reprog  *regcomplit(char *exp)

       Reprog  *regcompnl(char *exp)

       int  regexec(Reprog *prog, char *string, Resub *match, int msize)

       void regsub(char *source, char *dest, Resub *match, int msize)

       int  rregexec(Reprog *prog, Rune *string, Resub *match, int msize)

       void rregsub(Rune *source, Rune *dest, Resub *match, int msize)

       void regerror(char *msg)

DESCRIPTION

       Regcomp	compiles  a regular expression and returns a pointer to the generated description.  The space is allocated by malloc(2) and may be
       released by free.  Regular expressions are exactly as in regexp(6).

       Regcomplit is like regcomp except that all characters are treated literally.  Regcompnl is like regcomp except that  the  .   metacharacter
       matches all characters, including newlines.

       Regexec	matches  a  null-terminated string against the compiled regular expression in prog.  If it matches, regexec returns 1 and fills in
       the array match with character pointers to the substrings of string that correspond to the parenthesized subexpressions of exp: match[i].sp
       points to the beginning and match[i].ep points just beyond the end of the ith substring.  (Subexpression i begins at the ith left parenthe-
       sis, counting from 1.)  Pointers in match[0] pick out the substring that corresponds to the whole regular expression.  Unused  elements	of
       match  are  filled  with  zeros.  Matches involving and are extended as far as possible.  The number of array elements in match is given by
       msize.  The structure of elements of match is:

	      typedef struct {
		      union {
			 char *sp;
			 Rune *rsp;
		      };
		      union {
			 char *ep;
			 Rune *rep;
		      };
	      } Resub;

       If match[0].sp is nonzero on entry, regexec starts matching at that point within string.  If match[0].ep is  nonzero  on  entry,  the  last
       character matched is the one preceding that point.

       Regsub  places  in  dest  a substitution instance of source in the context of the last regexec performed using match.  Each instance of 
,
       where n is a digit, is replaced by the string delimited by match[n].sp and match[n].ep.	Each instance of is replaced by the string  delim-
       ited by match[0].sp and match[0].ep.

       Regerror,  called whenever an error is detected in regcomp, regexec, or regsub, writes the string msg on the standard error file and exits.
       Regerror can be replaced to perform special error processing.

       Rregexec and rregsub are variants of regexec and regsub that use strings of Runes instead of strings of chars.  With  these  routines,  the
       rsp and rep fields of the match array elements should be used.

SOURCE

       /sys/src/libregexp

SEE ALSO

       grep(1)

DIAGNOSTICS

       Regcomp returns 0 for an illegal expression or other failure.  Regexec returns 0 if string is not matched.

BUGS

       There is no way to specify or match a NUL character; NULs terminate patterns and strings.

																	 REGEXP(2)