Interface status:

externallyDefinedApi

REG_EXTENDED 0001

Description

regcomp(regex_t *,const char *,int)regcomp(regex_t *,const char *,int) flags. Use Extended Regular Expressions.

Interface status:

externallyDefinedApi

REG_ICASE 0002

Description

regcomp(regex_t *,const char *,int)regcomp(regex_t *,const char *,int) flags. Ignore case in match.

Interface status:

externallyDefinedApi

REG_NOSUB 0004

Description

regcomp(regex_t *,const char *,int)regcomp(regex_t *,const char *,int) flags. Report only success or fail in regexec(const regex_t *,const char *,size_t,regmatch_t *,int).

Interface status:

externallyDefinedApi

REG_NEWLINE 0010

Description

regcomp(regex_t *,const char *,int)regcomp(regex_t *,const char *,int) flags. Change the handling of s.

Interface status:

externallyDefinedApi

REG_ENOSYS (-1)

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags

Interface status:

externallyDefinedApi

REG_NOMATCH 1

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. regexec(const regex_t *,const char *,size_t,regmatch_t *,int) failed to match.

Interface status:

externallyDefinedApi

REG_BADPAT 2

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. Invalid regular expression.

Interface status:

externallyDefinedApi

REG_ECOLLATE 3

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. Invalid collating element referenced.

Interface status:

externallyDefinedApi

REG_ECTYPE 4

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. Invalid character class type referenced.

Interface status:

externallyDefinedApi

REG_EESCAPE 5

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. Trailing 'backslash' in pattern.

Interface status:

externallyDefinedApi

REG_ESUBREG 6

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. Number in "\\digit" invalid or in error.

Interface status:

externallyDefinedApi

REG_EBRACK 7

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. "[]" imbalance.

Interface status:

externallyDefinedApi

REG_EPAREN 8

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. "\(\)" or "()" imbalance.

Interface status:

externallyDefinedApi

REG_EBRACE 9

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. "" imbalance.

Interface status:

externallyDefinedApi

REG_BADBR 10

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. Content of "" invalid: not a number, number too large, more than two numbers, first larger than second.

Interface status:

externallyDefinedApi

REG_ERANGE 11

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags. Invalid endpoint in range expression.

Interface status:

externallyDefinedApi

REG_ESPACE 12

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags.Out of memory.

Interface status:

externallyDefinedApi

REG_BADRPT 13

Description

regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) flags

Interface status:

externallyDefinedApi

REG_NOTBOL 00001

Description

regexec(const regex_t *,const char *,size_t,regmatch_t *,int) flags. 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, shall not match the beginning of string.

Interface status:

externallyDefinedApi

REG_NOTEOL 00002

Description

regexec(const regex_t *,const char *,size_t,regmatch_t *,int) flags. 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, shall not match the end of string.

Interface status:

externallyDefinedApi

typedef __off_t regoff_t;

Description

signed arithmetic type that can hold the largest value that can be stored in either a type off_t or type ssize_t.

Interface status:

externallyDefinedApi

IMPORT_C int regcomp(regex_t *, const char *, int);

Description

regcomp function returns zero for a successful compilation or an error code for failure.

regexec function returns zero for a successful match or REG_NOMATCH for failure.

These routines implement regular expressions ("REs.") The regcomp function compiles an RE written as a string into an internal form, regexec matches that internal form against a string and reports results, regerror transforms error codes from either into human-readable messages, and regfree frees any dynamically-allocated storage used by the internal form of an RE.

The header   #include <regex.h>declares two structure types,  
  regex_t and  
  regmatch_t, the former for compiled internal forms and the latter for match reporting. It also declares the four functions, a type  
  regoff_t, and a number of constants with names starting with "REG_." 
The regcomp function compiles the regular expression contained in the pattern string, subject to the flags in cflags, and places the results in the 
regex_t structure pointed to by preg. The cflags argument is the bitwise OR of zero or more of the following flags: REG_EXTENDED  
Compile modern ("extended") REs, rather than the obsolete ("basic") REs that are the default.  
REG_BASIC  This is a synonym for 0, provided as a counterpart to REG_EXTENDED to improve readability.  
REG_NOSPEC  Compile with recognition of all special characters turned off. All characters are thus considered ordinary, so the "RE" is a literal string. This is an extension, compatible with but not specified by, and should be used with caution in software intended to be portable to other systems. REG_EXTENDED and REG_NOSPEC may not be used in the same call to regcomp.  
REG_ICASE  Compile for matching that ignores upper/lower case distinctions.  
REG_NOSUB  Compile for matching that need only report success or failure, not what was matched.  
REG_NEWLINE  Compile for newline-sensitive matching. By default, newline is a completely ordinary character with no special meaning in either REs or strings. With this flag, ‘[^’ bracket expressions and ‘.’ never match newline, a ‘^’ anchor matches the null string after any newline in the string in addition to its normal function, and the ‘$’ anchor matches the null string before any newline in the string in addition to its normal function.  
REG_PEND  The regular expression ends, not at the first NUL, but just before the character pointed to by the re_endp member of the structure pointed to by preg. The re_endp member is of type  
const char *. This flag permits inclusion of NULs in the RE; they are considered ordinary characters.  

When successful, regcomp returns 0 and fills in the structure pointed to by preg. One member of that structure (other than re_endp) is publicized: re_nsub, of type

size_t, contains the number of parenthesized subexpressions within the RE (except that the value of this member is undefined if the REG_NOSUB flag was used). If regcomp fails, it returns a non-zero error code; see DIAGNOSTICS. The regexec function matches the compiled RE pointed to by preg against the string, subject to the flags in eflags, and reports results using nmatch, pmatch, and the returned value. The RE must have been compiled by a previous invocation of regcomp. The compiled form is not altered during execution of regexec, so a single compiled RE can be used simultaneously by multiple threads.

By default, the NUL-terminated string pointed to by string is considered to be the text of an entire line, minus any terminating newline. The eflags argument is the bitwise OR of zero or more of the following flags: REG_NOTBOL The first character of the string is not the beginning of a line, so the ‘^’ anchor should not match before it. This does not affect the behavior of newlines under REG_NEWLINE. REG_NOTEOL The NUL terminating the string does not end a line, so the ‘$’ anchor should not match before it. This does not affect the behavior of newlines under REG_NEWLINE. REG_STARTEND The string is considered to start at string + pmatch [0]. rm_so and to have a terminating NUL located at string + pmatch [0]. rm_eo (there need not actually be a NUL at that location), regardless of the value of nmatch. See below for the definition of pmatch and nmatch. Note that a non-zero rm_so does not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not how it is matched.

Normally, regexec returns 0 for success and the non-zero code REG_NOMATCH for failure. Other non-zero error codes may be returned in exceptional situations; see DIAGNOSTICS.

If REG_NOSUB was specified in the compilation of the RE, or if nmatch is 0, regexec ignores the pmatch argument (but see below for the case where REG_STARTEND is specified). Otherwise, pmatch points to an array of nmatch structures of type

regmatch_tregmatch_t. Such a structure has at least the members rm_so and rm_eo, both of type regoff_t (a signed arithmetic type at least as large as an off_t and a ssize_t), containing respectively the offset of the first character of a substring and the offset of the first character after the end of the substring. Offsets are measured from the beginning of the string argument given to regexec. An empty substring is denoted by equal offsets, both indicating the character following the empty substring.

The 0th member of the pmatch array is filled in to indicate what substring of string was matched by the entire RE. Remaining members report what substring was matched by parenthesized subexpressions within the RE; member i reports subexpression i, with subexpressions counted (starting at 1) by the order of their opening parentheses in the RE, left to right. Unused entries in the array (corresponding either to subexpressions that did not participate in the match at all, or to subexpressions that do not exist in the RE (that is, i > preg -> re_nsub)) have both rm_so and rm_eo set to -1. If a subexpression participated in the match several times, the reported substring is the last one it matched. (Note, as an example in particular, that when the RE ‘(b*)+’ matches ‘bbb,’ the parenthesized subexpression matches each of the three 'bs' and then an infinite number of empty strings following the last ‘b,’ so the reported substring is one of the empties.) 

If REG_STARTEND is specified, pmatch must point to at least one

regmatch_tregmatch_t (even if nmatch is 0 or REG_NOSUB was specified), to hold the input offsets for REG_STARTEND. Use for output is still entirely controlled by nmatch; if nmatch is 0 or REG_NOSUB was specified, the value of pmatch [0] will not be changed by a successful regexec. The regerror function maps a non-zero errcode from either regcomp or regexec to a human-readable, printable message. If preg is non- NULL, the error code should have arisen from use of the

regex_tregex_t pointed to by preg, and if the error code came from regcomp, it should have been the result from the most recent regcomp using that regex_tregex_t. The ( (regerror); may be able to supply a more detailed message using information from the regex_tregex_t.) The regerror function places the NUL-terminated message into the buffer pointed to by errbuf, limiting the length (including the NUL) to at most errbuf_size bytes. If the whole message will not fit, as much of it as will fit before the terminating NUL is supplied. In any case, the returned value is the size of buffer needed to hold the whole message (including terminating NUL). If errbuf_size is 0, errbuf is ignored but the return value is still correct. If the errcode given to regerror is first ORed with REG_ITOA, the "message" that results is the printable name of the error code, e.g. "REG_NOMATCH," rather than an explanation thereof. If errcode is REG_ATOI, then preg shall be non- NULL and the re_endp member of the structure it points to must point to the printable name of an error code; in this case, the result in errbuf is the decimal digits of the numeric value of the error code (0 if the name is not recognized). REG_ITOA and REG_ATOI are intended primarily as debugging facilities

The regfree function frees any dynamically-allocated storage associated with the compiled RE pointed to by preg. The remaining

regex_tregex_t is no longer a valid compiled RE and the effect of supplying it to regexec or regerror is undefined. None of these functions references global variables except for tables of constants; all are safe for use from multiple threads if the arguments are safe.

Examples:

#include <stdio.h>
#include <regex.h>
int main()
{
   int ret,match=0;
   regex_t re;
   char errbuf[256];
   ret=regcomp(&re;,"[a-c]",REG_EXTENDED|REG_NOSUB);
   if(ret)
   {
      regerror(ret,&re;,errbuf,sizeof(errbuf));
      printf("compilation failed with error %s
",errbuf);
   }
   else
   {
      match=regexec(&re;,"access.txt|log.txt|passwd.txt",0,NULL,0);
      if(!match) printf("match found
");
      else printf("match not found");
      regfree(&re;);
   }
   return 0;
}

Output

match found

Diagnostics:

Non-zero error codes from regcomp and regexec include the following: REG_NOMATCH The regexec function
failed to match REG_BADPAT invalid regular expression REG_ECOLLATE   invalid collating element REG_ECTYPE invalid character class REG_EESCAPE ' \ '
applied to unescapable character REG_ESUBREG invalid backreference number REG_EBRACK brackets ' [ ] '
not balanced REG_EPAREN parentheses ' ( ) '
not balanced REG_EBRACE braces ' { } '
not balanced REG_BADBR invalid repetition count(s) in ' { } ' REG_ERANGE invalid character range in ' [ ] ' REG_ESPACE ran out of memory REG_BADRPT ' ?, ' ' *, '
or ' + '
operand invalid REG_EMPTY empty (sub)expression REG_ASSERT cannot happen - you found a bug REG_INVARG invalid argument, e.g. negative-length string REG_ILLSEQ illegal byte sequence (bad multibyte character) 
 Non-zero error codes from regcomp and regexec include the following: REG_NOMATCH The regexec function
failed to match REG_BADPAT invalid regular expression REG_ECOLLATE   invalid collating element REG_ECTYPE invalid character class REG_EESCAPE ' \ '
applied to unescapable character REG_ESUBREG invalid backreference number REG_EBRACK brackets ' [ ] '
not balanced REG_EPAREN parentheses ' ( ) '
not balanced REG_EBRACE braces ' { } '
not balanced REG_BADBR invalid repetition count(s) in ' { } ' REG_ERANGE invalid character range in ' [ ] ' REG_ESPACE ran out of memory REG_BADRPT ' ?, ' ' *, '
or ' + '
operand invalid REG_EMPTY empty (sub)expression REG_ASSERT cannot happen - you found a bug REG_INVARG invalid argument, e.g. negative-length string REG_ILLSEQ illegal byte sequence (bad multibyte character) 

Parameters

regex_tregex_t * const char * int Note: This description also covers the following functions - regexec(const regex_t *,const char *,size_t,regmatch_t *,int) regerror(int,const regex_t *,char *,size_t)regerror(int,const regex_t *,char *,size_t) regfree(regex_t *)regfree(regex_t *)

Return value

int regcomp function returns zero for a successful compilation or an error code for failure. regexec function returns zero for a successful match or REG_NOMATCH for failure.

Interface status:

externallyDefinedApi

IMPORT_C size_t regerror(int, const regex_t *, char *, size_t);

Description

Parameters

int const regex_tregex_t * char * size_tsize_t Refer to regcomp(regex_t *,const char *,int)regcomp(regex_t *,const char *,int) for the documentation

Return value

size_tsize_t

Interface status:

externallyDefinedApi

IMPORT_C void regfree(regex_t *);

Description

Parameters

regex_tregex_t * Refer to regcomp(regex_t *,const char *,int)regcomp(regex_t *,const char *,int) for the documentation