0.可参考关键字
C语言中的正则
C++中的正则
boost中的正则
1.四个重要函数及一些定义
REGEX(3) Linux Programmer's Manual
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);
1.1 regcomp-编译正则表达式
int regcomp(regex_t *preg, const char *regex, int cflags);
POSIX regex compiling
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 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
Do not report position of matches. The nmatch and pmatch arguments
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 nonmatching 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 REG_NOTEOL.
RETURN VALUE
regcomp() returns zero for a successful compilation or an error code for failure.1.2 regexec-匹配正则表达式
POSIX regex matching
int regexec(const regex_t *preg, const char *string, size_t nmatch,regmatch_t pmatch[], int eflags);
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 behavior 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)
RETURN VALUE
regexec() returns zero for a successful match or REG_NOMATCH for failure.
ERRORS
The following errors can be returned by regcomp():
REG_BADBR Invalid use of back reference operator.
REG_BADPAT Invalid use of pattern operators such as group or list.
REG_BADRPT Invalid use of repetition operators such as using '*' as
the first character.
REG_EBRACE Un-matched brace interval operators.
REG_EBRACK Un-matched bracket list operators.
REG_ECOLLATE Invalid collating element.
REG_ECTYPE Unknown character class name.
REG_EEND Nonspecific error. This is not defined by POSIX.2.
REG_EESCAPE Trailing backslash.
REG_EPAREN Un-matched parenthesis group operators.
REG_ERANGE Invalid use of the range operator, e.g., the ending point of the range
occurs prior to the starting point.
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.
REG_ESUBREG Invalid back reference to a subexpression.
1.3 regerror-翻译正则匹配过程中的错误信息
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 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 nonzero, errbuf is filled
in with the first errbuf_size - 1 characters of the error message and a terminating
null byte ('\0').1.4 regfree-释放正则匹配过程中的资源
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().
1.5 regmatch_t结构体
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, which is the offset of the first character after the matching
text.
typedef int regoff_t;