REGEXP(2) 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, int dlen, Resub *match, int msize)
int rregexec(Reprog *prog, Rune *string, Resub *match, int msize)
void rregsub(Rune *source, Rune *dest, int dlen, 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 new-
lines.
Regexec matches a null-terminated string against the com-
piled regular expression in prog. If it matches, regexec
returns 1 and fills in the array match with character point-
ers 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
parenthesis, 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:
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REGEXP(2) REGEXP(2)
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 \n, 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 delimited by
match[0].sp and match[0].ep. The substitution will always
be null terminated and trimmed to fit into dlen bytes.
Regerror, called whenever an error is detected in regcomp,
writes the string msg on the standard error file and exits.
Regerror can be replaced to perform special error process-
ing. If the user supplied regerror returns rather than
exits, regcomp will return 0.
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 fail-
ure. 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. The size of a character
class and the number of sub-expression matches are hard-
coded limits. The library uses the worst-case space estimate
for allocating VM runtime threads.
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REGEXP(2) REGEXP(2)
HISTORY
Regexp(2) first appeared in Plan 9 from Bell Labs. This
implementation was written from scratch for 9front (May,
2016).
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