NAME
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regcomp, regcomplit, regcompnl, regexec, regsub, rregexec, rregsub,
regfree, regerror – match regular expression |
SYNOPSIS
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#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 regfree(Reprog *prog)
void regerror(char *msg) |
DESCRIPTION
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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 regfree. 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 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:
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 NUL–terminated and trimmed to fit into dlen bytes. Regfree frees any dynamically–allocated storage associated with prog, and prog itself. 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 processing. 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
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/sys/src/libregexp |
SEE ALSO
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grep(1) |
DIAGNOSTICS
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Regcomp returns 0 for an illegal expression or other failure.
Regexec returns 0 if string is not matched. |
BUGS
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There is no way to specify or match a NUL character; NULs terminate
patterns and strings. This implementation uses some global variables, so beware of concurrent compilation. There is a fairly generous limit on the number of ranges in a character class (e.g., 256).
Regfree must be called to free dynamically allocated character–class
ranges; otherwise that memory will leak. |