Standard C Library Functions regcomp(3C)
NAME
regcomp, regexec, regerror, regfree - regular expression
matchingSYNOPSIS
#include
#include
int regcomp(regex_t *restrict preg, const char *restrict pattern,
int cflags);int regexec(const regex_t *restrict preg,
const char *restrict string, size_t nmatch,
regmatch_t pmatch[restrict], int eflags);
size_t regerror(int errcode, const regex_t *restrict preg,
char *restrict errbuf, size_t errbuf_size);
void regfree(regex_t *preg);
DESCRIPTION
These functions interpret basic and extended regular expres-
sions (described on the regex(5) manual page).The structure type regex_t contains at least the following
member:size_t re_nsub Number of parenthesised subexpressions.
The structure type regmatch_t contains at least the follow-
ing members:regoff_t rm_so Byte offset from start of string to start
of substring.regoff_t rm_eo Byte offset from start of string of the
first character after the end of sub-
string. regcomp() The regcomp() function will compile the regular expression contained in the string pointed to by the pattern argument and place the results in the structure pointed to by preg.SunOS 5.11 Last change: 1 Nov 2003 1
Standard C Library Functions regcomp(3C) The cflags argument is the bitwise inclusive OR of zero or more of the following flags, which are defined in the header: REG_EXTENDED Use Extended Regular Expressions.
REG_ICASE Ignore case in match.
REG_NOSUB Report only success/fail in regexec().
REG_NEWLINE Change the handling of NEWLINE characters,
as described in the text. The default regular expression type for pattern is a Basic Regular Expression. The application can specify ExtendedRegular Expressions using the REG_EXTENDED cflags flag.
If the REG_NOSUB flag was not set in cflags, then regcomp()
will set re_nsub to the number of parenthesised subexpres-
sions (delimited by \(\) in basic regular expressions or () in extended regular expressions) found in pattern. regexec()The regexec() function compares the null-terminated string
specified by string with the compiled regular expression preg initialized by a previous call to regcomp(). The eflags argument is the bitwise inclusive OR of zero or more of the following flags, which are defined in the header: REG_NOTBOL The first character of the string pointed to
by string is not the beginning of the line. Therefore, the circumflex character (^), when taken as a special character, will not match the beginning of string.REG_NOTEOL The last character of the string pointed to by
string is not the end of the line. Therefore,the dollar sign ($), when taken as a special
character, will not match the end of string.If nmatch is zero or REG_NOSUB was set in the cflags argu-
ment to regcomp(), then regexec() will ignore the pmatch argument. Otherwise, the pmatch argument must point to anSunOS 5.11 Last change: 1 Nov 2003 2
Standard C Library Functions regcomp(3C) array with at least nmatch elements, and regexec() will fill in the elements of that array with offsets of the substringsof string that correspond to the parenthesised subexpres-
sions of pattern: pmatch[i].rm_so will be the byte offset of
the beginning and pmatch[i].rm_eo will be one greater than
the byte offset of the end of substring i. (Subexpression i begins at the ith matched open parenthesis, counting from 1.) Offsets in pmatch[0] identify the substring thatcorresponds to the entire regular expression. Unused ele-
ments of pmatch up to pmatch[nmatch-1] will be filled with
-1. If there are more than nmatch subexpressions in pattern
(pattern itself counts as a subexpression), then regexec() will still do the match, but will record only the first nmatch substrings. When matching a basic or extended regular expression, anygiven parenthesised subexpression of pattern might partici-
pate in the match of several different substrings of string, or it might not match any substring even though the patternas a whole did match. The following rules are used to deter-
mine which substrings to report in pmatch when matching reg-
ular expressions:1. If subexpression i in a regular expression is not con-
tained within another subexpression, and it partici-
pated in the match several times, then the byte offsets in pmatch[i] will delimit the last such match. 2. If subexpression i is not contained within anothersubexpression, and it did not participate in an other-
wise successful match, the byte offsets in pmatch[i]will be -1. A subexpression does not participate in
the match when: * or \{\} appears immediately after the subexpression in a basic regular expression, or *, ?, or {} appears immediately after the subexpression in an extended regular expression, and the subexpression did not match (matched zero times) or | is used in an extended regular expression to selectthis subexpression or another, and the other subex-
pression matched.3. If subexpression i is contained within another subex-
pression j, and i is not contained within any other subexpression that is contained within j, and a matchSunOS 5.11 Last change: 1 Nov 2003 3
Standard C Library Functions regcomp(3C) of subexpression j is reported in pmatch[j], then thematch or non-match of subexpression i reported in
pmatch[i] will be as described in 1. and 2. above, but within the substring reported in pmatch[j] rather than the whole string. 4. If subexpression i is contained in subexpression j,and the byte offsets in pmatch[j] are -1, then the
pointers in pmatch[i] also will be -1.
5. If subexpression i matched a zero-length string, then
both byte offsets in pmatch[i] will be the byte offsetof the character or NULL terminator immediately fol-
lowing the zero-length string.
If, when regexec() is called, the locale is different from when the regular expression was compiled, the result is undefined.If REG_NEWLINE is not set in cflags, then a NEWLINE charac-
ter in pattern or string will be treated as an ordinarycharacter. If REG_NEWLINE is set, then newline will be
treated as an ordinary character except as follows: 1. A NEWLINE character in string will not be matched by a period outside a bracket expression or by any form ofa non-matching list.
2. A circumflex (^) in pattern, when used to specifyexpression anchoring will match the zero-length string
immediately after a newline in string, regardless ofthe setting of REG_NOTBOL.
3. A dollar-sign ($) in pattern, when used to specify
expression anchoring, will match the zero-length
string immediately before a newline in string, regard-
less of the setting of REG_NOTEOL.
regfree()
The regfree() function frees any memory allocated by
regcomp() associated with preg.SunOS 5.11 Last change: 1 Nov 2003 4
Standard C Library Functions regcomp(3C) The following constants are defined as error return values:REG_NOMATCH The regexec() function failed to match.
REG_BADPAT Invalid regular expression.
REG_ECOLLATE Invalid collating element referenced.
REG_ECTYPE Invalid character class type referenced.
REG_EESCAPE Trailing \ in pattern.
REG_ESUBREG Number in \digit invalid or in error.
REG_EBRACK [] imbalance.
REG_ENOSYS The function is not supported.
REG_EPAREN \(\) or () imbalance.
REG_EBRACE \{ \} imbalance.
REG_BADBR Content of \{ \} invalid: not a number,
number too large, more than two numbers, first larger than second.REG_ERANGE Invalid endpoint in range expression.
REG_ESPACE Out of memory.
REG_BADRPT ?, * or + not preceded by valid regular
expression. regerror() The regerror() function provides a mapping from error codes returned by regcomp() and regexec() to unspecified printable strings. It generates a string corresponding to the value ofthe errcode argument, which must be the last non-zero value
SunOS 5.11 Last change: 1 Nov 2003 5
Standard C Library Functions regcomp(3C) returned by regcomp() or regexec() with the given value ofpreg. If errcode is not such a value, an error message indi-
cating that the error code is invalid is returned. If preg is a NULL pointer, but errcode is a value returned by a previous call to regexec() or regcomp(), the regerror() still generates an error string corresponding to the value of errcode.If the errbuf_size argument is not zero, regerror() will
place the generated string into the buffer of sizeerrbuf_size bytes pointed to by errbuf. If the string
(including the terminating NULL) cannot fit in the buffer,regerror() will truncate the string and null-terminate the
result.If errbuf_size is zero, regerror() ignores the errbuf argu-
ment, and returns the size of the buffer needed to hold the generated string.If the preg argument to regexec() or regfree() is not a com-
piled regular expression returned by regcomp(), the resultis undefined. A preg is no longer treated as a compiled reg-
ular expression after it is given to regfree().
See regex(5) for BRE (Basic Regular Expression) Anchoring.RETURN VALUES
On successful completion, the regcomp() function returns 0. Otherwise, it returns an integer value indicating an erroras described in
fined. On successful completion, the regexec() function returns 0., and the content of preg is unde- Otherwise it returns REG_NOMATCH to indicate no match, or
REG_ENOSYS to indicate that the function is not supported.
Upon successful completion, the regerror() function returns the number of bytes needed to hold the entire generatedstring. Otherwise, it returns 0 to indicate that the func-
tion is not implemented.The regfree() function returns no value.
SunOS 5.11 Last change: 1 Nov 2003 6
Standard C Library Functions regcomp(3C)ERRORS
No errors are defined.USAGE
An application could use:regerror(code,preg,(char *)NULL,(size_t)0)
to find out how big a buffer is needed for the generated string, malloc a buffer to hold the string, and then callregerror() again to get the string (see malloc(3C)). Alter-
nately, it could allocate a fixed, static buffer that is bigenough to hold most strings, and then use malloc() to allo-
cate a larger buffer if it finds that this is too small.EXAMPLES
Example 1 Example to match string against the extended regu-
lar expression in pattern.#include
/* * Match string against the extended regular expression in * pattern, treating errors as no match. * * return 1 for match, 0 for no match */ int match(const char *string, char *pattern) { int status;regex_t re;
if (regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB) != 0) {
return(0); /* report error */ }status = regexec(&re, string, (size_t) 0, NULL, 0);
regfree(&re);
if (status != 0) { return(0); /* report error */ } return(1); }The following demonstrates how the REG_NOTBOL flag could be
used with regexec() to find all substrings in a line that match a pattern supplied by a user. (For simplicity of the example, very little error checking is done.)SunOS 5.11 Last change: 1 Nov 2003 7
Standard C Library Functions regcomp(3C) (void) regcomp (&re, pattern, 0); /* this call to regexec() finds the first match on the line */ error = regexec (&re, &buffer[0], 1, &pm, 0); while (error == 0) { /* while matches found *//* substring found between pm.rm_so and pm.rm_eo */
/* This call to regexec() finds the next match */error = regexec (&re, buffer + pm.rm_eo, 1, &pm, REG_NOTBOL);
}ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| CSI | Enabled ||_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| MT-Level | MT-Safe with exceptions |
|_____________________________|_____________________________|
| Standard | See standards(5). ||_____________________________|_____________________________|
SEE ALSO
fnmatch(3C), glob(3C), malloc(3C), setlocale(3C), attri-
butes(5), standards(5), regex(5) NOTES The regcomp() function can be used safely in a multithreaded application as long as setlocale(3C) is not being called to change the locale.SunOS 5.11 Last change: 1 Nov 2003 8