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diff --git a/srclib/pcre/doc/pcreapi.3 b/srclib/pcre/doc/pcreapi.3 new file mode 100644 index 0000000000..42a4e59c96 --- /dev/null +++ b/srclib/pcre/doc/pcreapi.3 @@ -0,0 +1,1288 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE NATIVE API" +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP, +.ti +5n +.B const char **\fIerrptr\fP, int *\fIerroffset\fP, +.ti +5n +.B const unsigned char *\fItableptr\fP); +.PP +.br +.B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP, +.ti +5n +.B const char **\fIerrptr\fP); +.PP +.br +.B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.ti +5n +.B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP, +.ti +5n +.B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP); +.PP +.br +.B int pcre_copy_named_substring(const pcre *\fIcode\fP, +.ti +5n +.B const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, const char *\fIstringname\fP, +.ti +5n +.B char *\fIbuffer\fP, int \fIbuffersize\fP); +.PP +.br +.B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP, +.ti +5n +.B int \fIbuffersize\fP); +.PP +.br +.B int pcre_get_named_substring(const pcre *\fIcode\fP, +.ti +5n +.B const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, const char *\fIstringname\fP, +.ti +5n +.B const char **\fIstringptr\fP); +.PP +.br +.B int pcre_get_stringnumber(const pcre *\fIcode\fP, +.ti +5n +.B const char *\fIname\fP); +.PP +.br +.B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, int \fIstringnumber\fP, +.ti +5n +.B const char **\fIstringptr\fP); +.PP +.br +.B int pcre_get_substring_list(const char *\fIsubject\fP, +.ti +5n +.B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);" +.PP +.br +.B void pcre_free_substring(const char *\fIstringptr\fP); +.PP +.br +.B void pcre_free_substring_list(const char **\fIstringptr\fP); +.PP +.br +.B const unsigned char *pcre_maketables(void); +.PP +.br +.B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.ti +5n +.B int \fIwhat\fP, void *\fIwhere\fP); +.PP +.br +.B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int +.B *\fIfirstcharptr\fP); +.PP +.br +.B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP); +.PP +.br +.B char *pcre_version(void); +.PP +.br +.B void *(*pcre_malloc)(size_t); +.PP +.br +.B void (*pcre_free)(void *); +.PP +.br +.B void *(*pcre_stack_malloc)(size_t); +.PP +.br +.B void (*pcre_stack_free)(void *); +.PP +.br +.B int (*pcre_callout)(pcre_callout_block *); +. +. +.SH "PCRE API OVERVIEW" +.rs +.sp +PCRE has its own native API, which is described in this document. There is also +a set of wrapper functions that correspond to the POSIX regular expression API. +These are described in the +.\" HREF +\fBpcreposix\fP +.\" +documentation. +.P +The native API function prototypes are defined in the header file \fBpcre.h\fP, +and on Unix systems the library itself is called \fBlibpcre\fP. It can +normally be accessed by adding \fB-lpcre\fP to the command for linking an +application that uses PCRE. The header file defines the macros PCRE_MAJOR and +PCRE_MINOR to contain the major and minor release numbers for the library. +Applications can use these to include support for different releases of PCRE. +.P +The functions \fBpcre_compile()\fP, \fBpcre_study()\fP, and \fBpcre_exec()\fP +are used for compiling and matching regular expressions. A sample program that +demonstrates the simplest way of using them is provided in the file called +\fIpcredemo.c\fP in the source distribution. The +.\" HREF +\fBpcresample\fP +.\" +documentation describes how to run it. +.P +In addition to the main compiling and matching functions, there are convenience +functions for extracting captured substrings from a matched subject string. +They are: +.sp + \fBpcre_copy_substring()\fP + \fBpcre_copy_named_substring()\fP + \fBpcre_get_substring()\fP + \fBpcre_get_named_substring()\fP + \fBpcre_get_substring_list()\fP + \fBpcre_get_stringnumber()\fP +.sp +\fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also +provided, to free the memory used for extracted strings. +.P +The function \fBpcre_maketables()\fP is used to build a set of character tables +in the current locale for passing to \fBpcre_compile()\fP or \fBpcre_exec()\fP. +This is an optional facility that is provided for specialist use. Most +commonly, no special tables are passed, in which case internal tables that are +generated when PCRE is built are used. +.P +The function \fBpcre_fullinfo()\fP is used to find out information about a +compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only +some of the available information, but is retained for backwards compatibility. +The function \fBpcre_version()\fP returns a pointer to a string containing the +version of PCRE and its date of release. +.P +The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain +the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions, +respectively. PCRE calls the memory management functions via these variables, +so a calling program can replace them if it wishes to intercept the calls. This +should be done before calling any PCRE functions. +.P +The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also +indirections to memory management functions. These special functions are used +only when PCRE is compiled to use the heap for remembering data, instead of +recursive function calls. This is a non-standard way of building PCRE, for use +in environments that have limited stacks. Because of the greater use of memory +management, it runs more slowly. Separate functions are provided so that +special-purpose external code can be used for this case. When used, these +functions are always called in a stack-like manner (last obtained, first +freed), and always for memory blocks of the same size. +.P +The global variable \fBpcre_callout\fP initially contains NULL. It can be set +by the caller to a "callout" function, which PCRE will then call at specified +points during a matching operation. Details are given in the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +. +. +.SH MULTITHREADING +.rs +.sp +The PCRE functions can be used in multi-threading applications, with the +proviso that the memory management functions pointed to by \fBpcre_malloc\fP, +\fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the +callout function pointed to by \fBpcre_callout\fP, are shared by all threads. +.P +The compiled form of a regular expression is not altered during matching, so +the same compiled pattern can safely be used by several threads at once. +. +. +.SH "SAVING PRECOMPILED PATTERNS FOR LATER USE" +.rs +.sp +The compiled form of a regular expression can be saved and re-used at a later +time, possibly by a different program, and even on a host other than the one on +which it was compiled. Details are given in the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation. +. +. +.SH "CHECKING BUILD-TIME OPTIONS" +.rs +.sp +.B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP); +.PP +The function \fBpcre_config()\fP makes it possible for a PCRE client to +discover which optional features have been compiled into the PCRE library. The +.\" HREF +\fBpcrebuild\fP +.\" +documentation has more details about these optional features. +.P +The first argument for \fBpcre_config()\fP is an integer, specifying which +information is required; the second argument is a pointer to a variable into +which the information is placed. The following information is available: +.sp + PCRE_CONFIG_UTF8 +.sp +The output is an integer that is set to one if UTF-8 support is available; +otherwise it is set to zero. +.sp + PCRE_CONFIG_UNICODE_PROPERTIES +.sp +The output is an integer that is set to one if support for Unicode character +properties is available; otherwise it is set to zero. +.sp + PCRE_CONFIG_NEWLINE +.sp +The output is an integer that is set to the value of the code that is used for +the newline character. It is either linefeed (10) or carriage return (13), and +should normally be the standard character for your operating system. +.sp + PCRE_CONFIG_LINK_SIZE +.sp +The output is an integer that contains the number of bytes used for internal +linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values +allow larger regular expressions to be compiled, at the expense of slower +matching. The default value of 2 is sufficient for all but the most massive +patterns, since it allows the compiled pattern to be up to 64K in size. +.sp + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD +.sp +The output is an integer that contains the threshold above which the POSIX +interface uses \fBmalloc()\fP for output vectors. Further details are given in +the +.\" HREF +\fBpcreposix\fP +.\" +documentation. +.sp + PCRE_CONFIG_MATCH_LIMIT +.sp +The output is an integer that gives the default limit for the number of +internal matching function calls in a \fBpcre_exec()\fP execution. Further +details are given with \fBpcre_exec()\fP below. +.sp + PCRE_CONFIG_STACKRECURSE +.sp +The output is an integer that is set to one if internal recursion is +implemented by recursive function calls that use the stack to remember their +state. This is the usual way that PCRE is compiled. The output is zero if PCRE +was compiled to use blocks of data on the heap instead of recursive function +calls. In this case, \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are +called to manage memory blocks on the heap, thus avoiding the use of the stack. +. +. +.SH "COMPILING A PATTERN" +.rs +.sp +.B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP, +.ti +5n +.B const char **\fIerrptr\fP, int *\fIerroffset\fP, +.ti +5n +.B const unsigned char *\fItableptr\fP); +.P +The function \fBpcre_compile()\fP is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the \fIpattern\fP argument. A pointer to a single block of memory +that is obtained via \fBpcre_malloc\fP is returned. This contains the compiled +code and related data. The \fBpcre\fP type is defined for the returned block; +this is a typedef for a structure whose contents are not externally defined. It +is up to the caller to free the memory when it is no longer required. +.P +Although the compiled code of a PCRE regex is relocatable, that is, it does not +depend on memory location, the complete \fBpcre\fP data block is not +fully relocatable, because it may contain a copy of the \fItableptr\fP +argument, which is an address (see below). +.P +The \fIoptions\fP argument contains independent bits that affect the +compilation. It should be zero if no options are required. The available +options are described below. Some of them, in particular, those that are +compatible with Perl, can also be set and unset from within the pattern (see +the detailed description in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation). For these options, the contents of the \fIoptions\fP argument +specifies their initial settings at the start of compilation and execution. The +PCRE_ANCHORED option can be set at the time of matching as well as at compile +time. +.P +If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately. +Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns +NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual +error message. The offset from the start of the pattern to the character where +the error was discovered is placed in the variable pointed to by +\fIerroffset\fP, which must not be NULL. If it is, an immediate error is given. +.P +If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of +character tables that are built when PCRE is compiled, using the default C +locale. Otherwise, \fItableptr\fP must be an address that is the result of a +call to \fBpcre_maketables()\fP. This value is stored with the compiled +pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is +passed to it. For more discussion, see the section on locale support below. +.P +This code fragment shows a typical straightforward call to \fBpcre_compile()\fP: +.sp + pcre *re; + const char *error; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ +.sp +The following names for option bits are defined in the \fBpcre.h\fP header +file: +.sp + PCRE_ANCHORED +.sp +If this bit is set, the pattern is forced to be "anchored", that is, it is +constrained to match only at the first matching point in the string that is +being searched (the "subject string"). This effect can also be achieved by +appropriate constructs in the pattern itself, which is the only way to do it in +Perl. +.sp + PCRE_AUTO_CALLOUT +.sp +If this bit is set, \fBpcre_compile()\fP automatically inserts callout items, +all with number 255, before each pattern item. For discussion of the callout +facility, see the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +.sp + PCRE_CASELESS +.sp +If this bit is set, letters in the pattern match both upper and lower case +letters. It is equivalent to Perl's /i option, and it can be changed within a +pattern by a (?i) option setting. When running in UTF-8 mode, case support for +high-valued characters is available only when PCRE is built with Unicode +character property support. +.sp + PCRE_DOLLAR_ENDONLY +.sp +If this bit is set, a dollar metacharacter in the pattern matches only at the +end of the subject string. Without this option, a dollar also matches +immediately before the final character if it is a newline (but not before any +other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is +set. There is no equivalent to this option in Perl, and no way to set it within +a pattern. +.sp + PCRE_DOTALL +.sp +If this bit is set, a dot metacharater in the pattern matches all characters, +including newlines. Without it, newlines are excluded. This option is +equivalent to Perl's /s option, and it can be changed within a pattern by a +(?s) option setting. A negative class such as [^a] always matches a newline +character, independent of the setting of this option. +.sp + PCRE_EXTENDED +.sp +If this bit is set, whitespace data characters in the pattern are totally +ignored except when escaped or inside a character class. Whitespace does not +include the VT character (code 11). In addition, characters between an +unescaped # outside a character class and the next newline character, +inclusive, are also ignored. This is equivalent to Perl's /x option, and it can +be changed within a pattern by a (?x) option setting. +.P +This option makes it possible to include comments inside complicated patterns. +Note, however, that this applies only to data characters. Whitespace characters +may never appear within special character sequences in a pattern, for example +within the sequence (?( which introduces a conditional subpattern. +.sp + PCRE_EXTRA +.sp +This option was invented in order to turn on additional functionality of PCRE +that is incompatible with Perl, but it is currently of very little use. When +set, any backslash in a pattern that is followed by a letter that has no +special meaning causes an error, thus reserving these combinations for future +expansion. By default, as in Perl, a backslash followed by a letter with no +special meaning is treated as a literal. There are at present no other features +controlled by this option. It can also be set by a (?X) option setting within a +pattern. +.sp + PCRE_MULTILINE +.sp +By default, PCRE treats the subject string as consisting of a single line of +characters (even if it actually contains newlines). The "start of line" +metacharacter (^) matches only at the start of the string, while the "end of +line" metacharacter ($) matches only at the end of the string, or before a +terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as +Perl. +.P +When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs +match immediately following or immediately before any newline in the subject +string, respectively, as well as at the very start and end. This is equivalent +to Perl's /m option, and it can be changed within a pattern by a (?m) option +setting. If there are no "\en" characters in a subject string, or no +occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. +.sp + PCRE_NO_AUTO_CAPTURE +.sp +If this option is set, it disables the use of numbered capturing parentheses in +the pattern. Any opening parenthesis that is not followed by ? behaves as if it +were followed by ?: but named parentheses can still be used for capturing (and +they acquire numbers in the usual way). There is no equivalent of this option +in Perl. +.sp + PCRE_UNGREEDY +.sp +This option inverts the "greediness" of the quantifiers so that they are not +greedy by default, but become greedy if followed by "?". It is not compatible +with Perl. It can also be set by a (?U) option setting within the pattern. +.sp + PCRE_UTF8 +.sp +This option causes PCRE to regard both the pattern and the subject as strings +of UTF-8 characters instead of single-byte character strings. However, it is +available only when PCRE is built to include UTF-8 support. If not, the use +of this option provokes an error. Details of how this option changes the +behaviour of PCRE are given in the +.\" HTML <a href="pcre.html#utf8support"> +.\" </a> +section on UTF-8 support +.\" +in the main +.\" HREF +\fBpcre\fP +.\" +page. +.sp + PCRE_NO_UTF8_CHECK +.sp +When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is +automatically checked. If an invalid UTF-8 sequence of bytes is found, +\fBpcre_compile()\fP returns an error. If you already know that your pattern is +valid, and you want to skip this check for performance reasons, you can set the +PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid +UTF-8 string as a pattern is undefined. It may cause your program to crash. +Note that this option can also be passed to \fBpcre_exec()\fP, to suppress the +UTF-8 validity checking of subject strings. +. +. +.SH "STUDYING A PATTERN" +.rs +.sp +.B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP, +.ti +5n +.B const char **\fIerrptr\fP); +.PP +If a compiled pattern is going to be used several times, it is worth spending +more time analyzing it in order to speed up the time taken for matching. The +function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first +argument. If studying the pattern produces additional information that will +help speed up matching, \fBpcre_study()\fP returns a pointer to a +\fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the +results of the study. +.P +The returned value from \fBpcre_study()\fP can be passed directly to +\fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other +fields that can be set by the caller before the block is passed; these are +described +.\" HTML <a href="#extradata"> +.\" </a> +below +.\" +in the section on matching a pattern. +.P +If studying the pattern does not produce any additional information, +\fBpcre_study()\fP returns NULL. In that circumstance, if the calling program +wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its +own \fBpcre_extra\fP block. +.P +The second argument of \fBpcre_study()\fP contains option bits. At present, no +options are defined, and this argument should always be zero. +.P +The third argument for \fBpcre_study()\fP is a pointer for an error message. If +studying succeeds (even if no data is returned), the variable it points to is +set to NULL. Otherwise it points to a textual error message. You should +therefore test the error pointer for NULL after calling \fBpcre_study()\fP, to +be sure that it has run successfully. +.P +This is a typical call to \fBpcre_study\fP(): +.sp + pcre_extra *pe; + pe = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options exist */ + &error); /* set to NULL or points to a message */ +.sp +At present, studying a pattern is useful only for non-anchored patterns that do +not have a single fixed starting character. A bitmap of possible starting +bytes is created. +. +. +.\" HTML <a name="localesupport"></a> +.SH "LOCALE SUPPORT" +.rs +.sp +PCRE handles caseless matching, and determines whether characters are letters, +digits, or whatever, by reference to a set of tables, indexed by character +value. (When running in UTF-8 mode, this applies only to characters with codes +less than 128. Higher-valued codes never match escapes such as \ew or \ed, but +can be tested with \ep if PCRE is built with Unicode character property +support.) +.P +An internal set of tables is created in the default C locale when PCRE is +built. This is used when the final argument of \fBpcre_compile()\fP is NULL, +and is sufficient for many applications. An alternative set of tables can, +however, be supplied. These may be created in a different locale from the +default. As more and more applications change to using Unicode, the need for +this locale support is expected to die away. +.P +External tables are built by calling the \fBpcre_maketables()\fP function, +which has no arguments, in the relevant locale. The result can then be passed +to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For +example, to build and use tables that are appropriate for the French locale +(where accented characters with values greater than 128 are treated as letters), +the following code could be used: +.sp + setlocale(LC_CTYPE, "fr_FR"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); +.sp +When \fBpcre_maketables()\fP runs, the tables are built in memory that is +obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure +that the memory containing the tables remains available for as long as it is +needed. +.P +The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled +pattern, and the same tables are used via this pointer by \fBpcre_study()\fP +and normally also by \fBpcre_exec()\fP. Thus, by default, for any single +pattern, compilation, studying and matching all happen in the same locale, but +different patterns can be compiled in different locales. +.P +It is possible to pass a table pointer or NULL (indicating the use of the +internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose, +this facility could be used to match a pattern in a different locale from the +one in which it was compiled. Passing table pointers at run time is discussed +below in the section on matching a pattern. +. +. +.SH "INFORMATION ABOUT A PATTERN" +.rs +.sp +.B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.ti +5n +.B int \fIwhat\fP, void *\fIwhere\fP); +.PP +The \fBpcre_fullinfo()\fP function returns information about a compiled +pattern. It replaces the obsolete \fBpcre_info()\fP function, which is +nevertheless retained for backwards compability (and is documented below). +.P +The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled +pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if +the pattern was not studied. The third argument specifies which piece of +information is required, and the fourth argument is a pointer to a variable +to receive the data. The yield of the function is zero for success, or one of +the following negative numbers: +.sp + PCRE_ERROR_NULL the argument \fIcode\fP was NULL + the argument \fIwhere\fP was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid +.sp +The "magic number" is placed at the start of each compiled pattern as an simple +check against passing an arbitrary memory pointer. Here is a typical call of +\fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern: +.sp + int rc; + unsigned long int length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + pe, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ +.sp +The possible values for the third argument are defined in \fBpcre.h\fP, and are +as follows: +.sp + PCRE_INFO_BACKREFMAX +.sp +Return the number of the highest back reference in the pattern. The fourth +argument should point to an \fBint\fP variable. Zero is returned if there are +no back references. +.sp + PCRE_INFO_CAPTURECOUNT +.sp +Return the number of capturing subpatterns in the pattern. The fourth argument +should point to an \fBint\fP variable. +.sp + PCRE_INFO_DEFAULTTABLES +.sp +Return a pointer to the internal default character tables within PCRE. The +fourth argument should point to an \fBunsigned char *\fP variable. This +information call is provided for internal use by the \fBpcre_study()\fP +function. External callers can cause PCRE to use its internal tables by passing +a NULL table pointer. +.sp + PCRE_INFO_FIRSTBYTE +.sp +Return information about the first byte of any matched string, for a +non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the +old name is still recognized for backwards compatibility.) +.P +If there is a fixed first byte, for example, from a pattern such as +(cat|cow|coyote), it is returned in the integer pointed to by \fIwhere\fP. +Otherwise, if either +.sp +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +.sp +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +.sp +-1 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise -2 is +returned. For anchored patterns, -2 is returned. +.sp + PCRE_INFO_FIRSTTABLE +.sp +If the pattern was studied, and this resulted in the construction of a 256-bit +table indicating a fixed set of bytes for the first byte in any matching +string, a pointer to the table is returned. Otherwise NULL is returned. The +fourth argument should point to an \fBunsigned char *\fP variable. +.sp + PCRE_INFO_LASTLITERAL +.sp +Return the value of the rightmost literal byte that must exist in any matched +string, other than at its start, if such a byte has been recorded. The fourth +argument should point to an \fBint\fP variable. If there is no such byte, -1 is +returned. For anchored patterns, a last literal byte is recorded only if it +follows something of variable length. For example, for the pattern +/^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value +is -1. +.sp + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE +.sp +PCRE supports the use of named as well as numbered capturing parentheses. The +names are just an additional way of identifying the parentheses, which still +acquire numbers. A convenience function called \fBpcre_get_named_substring()\fP +is provided for extracting an individual captured substring by name. It is also +possible to extract the data directly, by first converting the name to a number +in order to access the correct pointers in the output vector (described with +\fBpcre_exec()\fP below). To do the conversion, you need to use the +name-to-number map, which is described by these three values. +.P +The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives +the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each +entry; both of these return an \fBint\fP value. The entry size depends on the +length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first +entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry +are the number of the capturing parenthesis, most significant byte first. The +rest of the entry is the corresponding name, zero terminated. The names are in +alphabetical order. For example, consider the following pattern (assume +PCRE_EXTENDED is set, so white space - including newlines - is ignored): +.sp +.\" JOIN + (?P<date> (?P<year>(\ed\ed)?\ed\ed) - + (?P<month>\ed\ed) - (?P<day>\ed\ed) ) +.sp +There are four named subpatterns, so the table has four entries, and each entry +in the table is eight bytes long. The table is as follows, with non-printing +bytes shows in hexadecimal, and undefined bytes shown as ??: +.sp + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? +.sp +When writing code to extract data from named subpatterns using the +name-to-number map, remember that the length of each entry is likely to be +different for each compiled pattern. +.sp + PCRE_INFO_OPTIONS +.sp +Return a copy of the options with which the pattern was compiled. The fourth +argument should point to an \fBunsigned long int\fP variable. These option bits +are those specified in the call to \fBpcre_compile()\fP, modified by any +top-level option settings within the pattern itself. +.P +A pattern is automatically anchored by PCRE if all of its top-level +alternatives begin with one of the following: +.sp + ^ unless PCRE_MULTILINE is set + \eA always + \eG always +.\" JOIN + .* if PCRE_DOTALL is set and there are no back + references to the subpattern in which .* appears +.sp +For such patterns, the PCRE_ANCHORED bit is set in the options returned by +\fBpcre_fullinfo()\fP. +.sp + PCRE_INFO_SIZE +.sp +Return the size of the compiled pattern, that is, the value that was passed as +the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to +place the compiled data. The fourth argument should point to a \fBsize_t\fP +variable. +.sp + PCRE_INFO_STUDYSIZE +.sp +Return the size of the data block pointed to by the \fIstudy_data\fP field in +a \fBpcre_extra\fP block. That is, it is the value that was passed to +\fBpcre_malloc()\fP when PCRE was getting memory into which to place the data +created by \fBpcre_study()\fP. The fourth argument should point to a +\fBsize_t\fP variable. +. +. +.SH "OBSOLETE INFO FUNCTION" +.rs +.sp +.B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int +.B *\fIfirstcharptr\fP); +.PP +The \fBpcre_info()\fP function is now obsolete because its interface is too +restrictive to return all the available data about a compiled pattern. New +programs should use \fBpcre_fullinfo()\fP instead. The yield of +\fBpcre_info()\fP is the number of capturing subpatterns, or one of the +following negative numbers: +.sp + PCRE_ERROR_NULL the argument \fIcode\fP was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found +.sp +If the \fIoptptr\fP argument is not NULL, a copy of the options with which the +pattern was compiled is placed in the integer it points to (see +PCRE_INFO_OPTIONS above). +.P +If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL, +it is used to pass back information about the first character of any matched +string (see PCRE_INFO_FIRSTBYTE above). +. +. +.SH "MATCHING A PATTERN" +.rs +.sp +.B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.ti +5n +.B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP, +.ti +5n +.B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP); +.P +The function \fBpcre_exec()\fP is called to match a subject string against a +compiled pattern, which is passed in the \fIcode\fP argument. If the +pattern has been studied, the result of the study should be passed in the +\fIextra\fP argument. +.P +In most applications, the pattern will have been compiled (and optionally +studied) in the same process that calls \fBpcre_exec()\fP. However, it is +possible to save compiled patterns and study data, and then use them later +in different processes, possibly even on different hosts. For a discussion +about this, see the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation. +.P +Here is an example of a simple call to \fBpcre_exec()\fP: +.sp + int rc; + int ovector[30]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 30); /* number of elements in the vector (NOT size in bytes) */ +. +.\" HTML <a name="extradata"></a> +.SS "Extra data for \fBpcre_exec()\fR" +.rs +.sp +If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP +data block. The \fBpcre_study()\fP function returns such a block (when it +doesn't return NULL), but you can also create one for yourself, and pass +additional information in it. The fields in a \fBpcre_extra\fP block are as +follows: +.sp + unsigned long int \fIflags\fP; + void *\fIstudy_data\fP; + unsigned long int \fImatch_limit\fP; + void *\fIcallout_data\fP; + const unsigned char *\fItables\fP; +.sp +The \fIflags\fP field is a bitmap that specifies which of the other fields +are set. The flag bits are: +.sp + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_CALLOUT_DATA + PCRE_EXTRA_TABLES +.sp +Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the +\fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with +the appropriate flag bit. You should not set this yourself, but you may add to +the block by setting the other fields and their corresponding flag bits. +.P +The \fImatch_limit\fP field provides a means of preventing PCRE from using up a +vast amount of resources when running patterns that are not going to match, +but which have a very large number of possibilities in their search trees. The +classic example is the use of nested unlimited repeats. +.P +Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly +(sometimes recursively). The limit is imposed on the number of times this +function is called during a match, which has the effect of limiting the amount +of recursion and backtracking that can take place. For patterns that are not +anchored, the count starts from zero for each position in the subject string. +.P +The default limit for the library can be set when PCRE is built; the default +default is 10 million, which handles all but the most extreme cases. You can +reduce the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP block +in which \fImatch_limit\fP is set to a smaller value, and +PCRE_EXTRA_MATCH_LIMIT is set in the \fIflags\fP field. If the limit is +exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_MATCHLIMIT. +.P +The \fIpcre_callout\fP field is used in conjunction with the "callout" feature, +which is described in the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +.P +The \fItables\fP field is used to pass a character tables pointer to +\fBpcre_exec()\fP; this overrides the value that is stored with the compiled +pattern. A non-NULL value is stored with the compiled pattern only if custom +tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument. +If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's +internal tables to be used. This facility is helpful when re-using patterns +that have been saved after compiling with an external set of tables, because +the external tables might be at a different address when \fBpcre_exec()\fP is +called. See the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation for a discussion of saving compiled patterns for later use. +. +.SS "Option bits for \fBpcre_exec()\fP" +.rs +.sp +The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be +zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NOTBOL, +PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL. +.sp + PCRE_ANCHORED +.sp +The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first +matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out +to be anchored by virtue of its contents, it cannot be made unachored at +matching time. +.sp + PCRE_NOTBOL +.sp +This option specifies that first character of the subject string is not the +beginning of a line, so the circumflex metacharacter should not match before +it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex +never to match. This option affects only the behaviour of the circumflex +metacharacter. It does not affect \eA. +.sp + PCRE_NOTEOL +.sp +This option specifies that the end of the subject string is not the end of a +line, so the dollar metacharacter should not match it nor (except in multiline +mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at +compile time) causes dollar never to match. This option affects only the +behaviour of the dollar metacharacter. It does not affect \eZ or \ez. +.sp + PCRE_NOTEMPTY +.sp +An empty string is not considered to be a valid match if this option is set. If +there are alternatives in the pattern, they are tried. If all the alternatives +match the empty string, the entire match fails. For example, if the pattern +.sp + a?b? +.sp +is applied to a string not beginning with "a" or "b", it matches the empty +string at the start of the subject. With PCRE_NOTEMPTY set, this match is not +valid, so PCRE searches further into the string for occurrences of "a" or "b". +.P +Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case +of a pattern match of the empty string within its \fBsplit()\fP function, and +when using the /g modifier. It is possible to emulate Perl's behaviour after +matching a null string by first trying the match again at the same offset with +PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the +starting offset (see below) and trying an ordinary match again. There is some +code that demonstrates how to do this in the \fIpcredemo.c\fP sample program. +.sp + PCRE_NO_UTF8_CHECK +.sp +When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8 +string is automatically checked when \fBpcre_exec()\fP is subsequently called. +The value of \fIstartoffset\fP is also checked to ensure that it points to the +start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found, +\fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP +contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned. +.P +If you already know that your subject is valid, and you want to skip these +checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when +calling \fBpcre_exec()\fP. You might want to do this for the second and +subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find +all the matches in a single subject string. However, you should be sure that +the value of \fIstartoffset\fP points to the start of a UTF-8 character. When +PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a +subject, or a value of \fIstartoffset\fP that does not point to the start of a +UTF-8 character, is undefined. Your program may crash. +.sp + PCRE_PARTIAL +.sp +This option turns on the partial matching feature. If the subject string fails +to match the pattern, but at some point during the matching process the end of +the subject was reached (that is, the subject partially matches the pattern and +the failure to match occurred only because there were not enough subject +characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of +PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what +may appear in the pattern. These are discussed in the +.\" HREF +\fBpcrepartial\fP +.\" +documentation. +. +.SS "The string to be matched by \fBpcre_exec()\fP" +.rs +.sp +The subject string is passed to \fBpcre_exec()\fP as a pointer in +\fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in +\fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a +UTF-8 character. Unlike the pattern string, the subject may contain binary zero +bytes. When the starting offset is zero, the search for a match starts at the +beginning of the subject, and this is by far the most common case. +.P +A non-zero starting offset is useful when searching for another match in the +same subject by calling \fBpcre_exec()\fP again after a previous success. +Setting \fIstartoffset\fP differs from just passing over a shortened string and +setting PCRE_NOTBOL in the case of a pattern that begins with any kind of +lookbehind. For example, consider the pattern +.sp + \eBiss\eB +.sp +which finds occurrences of "iss" in the middle of words. (\eB matches only if +the current position in the subject is not a word boundary.) When applied to +the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first +occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the +subject, namely "issipi", it does not match, because \eB is always false at the +start of the subject, which is deemed to be a word boundary. However, if +\fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP +set to 4, it finds the second occurrence of "iss" because it is able to look +behind the starting point to discover that it is preceded by a letter. +.P +If a non-zero starting offset is passed when the pattern is anchored, one +attempt to match at the given offset is made. This can only succeed if the +pattern does not require the match to be at the start of the subject. +. +.SS "How \fBpcre_exec()\fP returns captured substrings" +.rs +.sp +In general, a pattern matches a certain portion of the subject, and in +addition, further substrings from the subject may be picked out by parts of the +pattern. Following the usage in Jeffrey Friedl's book, this is called +"capturing" in what follows, and the phrase "capturing subpattern" is used for +a fragment of a pattern that picks out a substring. PCRE supports several other +kinds of parenthesized subpattern that do not cause substrings to be captured. +.P +Captured substrings are returned to the caller via a vector of integer offsets +whose address is passed in \fIovector\fP. The number of elements in the vector +is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: +this argument is NOT the size of \fIovector\fP in bytes. +.P +The first two-thirds of the vector is used to pass back captured substrings, +each substring using a pair of integers. The remaining third of the vector is +used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns, +and is not available for passing back information. The length passed in +\fIovecsize\fP should always be a multiple of three. If it is not, it is +rounded down. +.P +When a match is successful, information about captured substrings is returned +in pairs of integers, starting at the beginning of \fIovector\fP, and +continuing up to two-thirds of its length at the most. The first element of a +pair is set to the offset of the first character in a substring, and the second +is set to the offset of the first character after the end of a substring. The +first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the +subject string matched by the entire pattern. The next pair is used for the +first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP +is the number of pairs that have been set. If there are no capturing +subpatterns, the return value from a successful match is 1, indicating that +just the first pair of offsets has been set. +.P +Some convenience functions are provided for extracting the captured substrings +as separate strings. These are described in the following section. +.P +It is possible for an capturing subpattern number \fIn+1\fP to match some +part of the subject when subpattern \fIn\fP has not been used at all. For +example, if the string "abc" is matched against the pattern (a|(z))(bc) +subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset +values corresponding to the unused subpattern are set to -1. +.P +If a capturing subpattern is matched repeatedly, it is the last portion of the +string that it matched that is returned. +.P +If the vector is too small to hold all the captured substring offsets, it is +used as far as possible (up to two-thirds of its length), and the function +returns a value of zero. In particular, if the substring offsets are not of +interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and +\fIovecsize\fP as zero. However, if the pattern contains back references and +the \fIovector\fP is not big enough to remember the related substrings, PCRE +has to get additional memory for use during matching. Thus it is usually +advisable to supply an \fIovector\fP. +.P +Note that \fBpcre_info()\fP can be used to find out how many capturing +subpatterns there are in a compiled pattern. The smallest size for +\fIovector\fP that will allow for \fIn\fP captured substrings, in addition to +the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3. +. +.SS "Return values from \fBpcre_exec()\fP" +.rs +.sp +If \fBpcre_exec()\fP fails, it returns a negative number. The following are +defined in the header file: +.sp + PCRE_ERROR_NOMATCH (-1) +.sp +The subject string did not match the pattern. +.sp + PCRE_ERROR_NULL (-2) +.sp +Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was +NULL and \fIovecsize\fP was not zero. +.sp + PCRE_ERROR_BADOPTION (-3) +.sp +An unrecognized bit was set in the \fIoptions\fP argument. +.sp + PCRE_ERROR_BADMAGIC (-4) +.sp +PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch +the case when it is passed a junk pointer and to detect when a pattern that was +compiled in an environment of one endianness is run in an environment with the +other endianness. This is the error that PCRE gives when the magic number is +not present. +.sp + PCRE_ERROR_UNKNOWN_NODE (-5) +.sp +While running the pattern match, an unknown item was encountered in the +compiled pattern. This error could be caused by a bug in PCRE or by overwriting +of the compiled pattern. +.sp + PCRE_ERROR_NOMEMORY (-6) +.sp +If a pattern contains back references, but the \fIovector\fP that is passed to +\fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE +gets a block of memory at the start of matching to use for this purpose. If the +call via \fBpcre_malloc()\fP fails, this error is given. The memory is +automatically freed at the end of matching. +.sp + PCRE_ERROR_NOSUBSTRING (-7) +.sp +This error is used by the \fBpcre_copy_substring()\fP, +\fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see +below). It is never returned by \fBpcre_exec()\fP. +.sp + PCRE_ERROR_MATCHLIMIT (-8) +.sp +The recursion and backtracking limit, as specified by the \fImatch_limit\fP +field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the +description above. +.sp + PCRE_ERROR_CALLOUT (-9) +.sp +This error is never generated by \fBpcre_exec()\fP itself. It is provided for +use by callout functions that want to yield a distinctive error code. See the +.\" HREF +\fBpcrecallout\fP +.\" +documentation for details. +.sp + PCRE_ERROR_BADUTF8 (-10) +.sp +A string that contains an invalid UTF-8 byte sequence was passed as a subject. +.sp + PCRE_ERROR_BADUTF8_OFFSET (-11) +.sp +The UTF-8 byte sequence that was passed as a subject was valid, but the value +of \fIstartoffset\fP did not point to the beginning of a UTF-8 character. +.sp + PCRE_ERROR_PARTIAL (-12) +.sp +The subject string did not match, but it did match partially. See the +.\" HREF +\fBpcrepartial\fP +.\" +documentation for details of partial matching. +.sp + PCRE_ERROR_BAD_PARTIAL (-13) +.sp +The PCRE_PARTIAL option was used with a compiled pattern containing items that +are not supported for partial matching. See the +.\" HREF +\fBpcrepartial\fP +.\" +documentation for details of partial matching. +.sp + PCRE_ERROR_INTERNAL (-14) +.sp +An unexpected internal error has occurred. This error could be caused by a bug +in PCRE or by overwriting of the compiled pattern. +.sp + PCRE_ERROR_BADCOUNT (-15) +.sp +This error is given if the value of the \fIovecsize\fP argument is negative. +. +. +.SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER" +.rs +.sp +.B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP, +.ti +5n +.B int \fIbuffersize\fP); +.PP +.br +.B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, int \fIstringnumber\fP, +.ti +5n +.B const char **\fIstringptr\fP); +.PP +.br +.B int pcre_get_substring_list(const char *\fIsubject\fP, +.ti +5n +.B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);" +.PP +Captured substrings can be accessed directly by using the offsets returned by +\fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions +\fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and +\fBpcre_get_substring_list()\fP are provided for extracting captured substrings +as new, separate, zero-terminated strings. These functions identify substrings +by number. The next section describes functions for extracting named +substrings. A substring that contains a binary zero is correctly extracted and +has a further zero added on the end, but the result is not, of course, +a C string. +.P +The first three arguments are the same for all three of these functions: +\fIsubject\fP is the subject string that has just been successfully matched, +\fIovector\fP is a pointer to the vector of integer offsets that was passed to +\fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were +captured by the match, including the substring that matched the entire regular +expression. This is the value returned by \fBpcre_exec()\fP if it is greater +than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of +space in \fIovector\fP, the value passed as \fIstringcount\fP should be the +number of elements in the vector divided by three. +.P +The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP +extract a single substring, whose number is given as \fIstringnumber\fP. A +value of zero extracts the substring that matched the entire pattern, whereas +higher values extract the captured substrings. For \fBpcre_copy_substring()\fP, +the string is placed in \fIbuffer\fP, whose length is given by +\fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is +obtained via \fBpcre_malloc\fP, and its address is returned via +\fIstringptr\fP. The yield of the function is the length of the string, not +including the terminating zero, or one of +.sp + PCRE_ERROR_NOMEMORY (-6) +.sp +The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get +memory failed for \fBpcre_get_substring()\fP. +.sp + PCRE_ERROR_NOSUBSTRING (-7) +.sp +There is no substring whose number is \fIstringnumber\fP. +.P +The \fBpcre_get_substring_list()\fP function extracts all available substrings +and builds a list of pointers to them. All this is done in a single block of +memory that is obtained via \fBpcre_malloc\fP. The address of the memory block +is returned via \fIlistptr\fP, which is also the start of the list of string +pointers. The end of the list is marked by a NULL pointer. The yield of the +function is zero if all went well, or +.sp + PCRE_ERROR_NOMEMORY (-6) +.sp +if the attempt to get the memory block failed. +.P +When any of these functions encounter a substring that is unset, which can +happen when capturing subpattern number \fIn+1\fP matches some part of the +subject, but subpattern \fIn\fP has not been used at all, they return an empty +string. This can be distinguished from a genuine zero-length substring by +inspecting the appropriate offset in \fIovector\fP, which is negative for unset +substrings. +.P +The two convenience functions \fBpcre_free_substring()\fP and +\fBpcre_free_substring_list()\fP can be used to free the memory returned by +a previous call of \fBpcre_get_substring()\fP or +\fBpcre_get_substring_list()\fP, respectively. They do nothing more than call +the function pointed to by \fBpcre_free\fP, which of course could be called +directly from a C program. However, PCRE is used in some situations where it is +linked via a special interface to another programming language which cannot use +\fBpcre_free\fP directly; it is for these cases that the functions are +provided. +. +. +.SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME" +.rs +.sp +.B int pcre_get_stringnumber(const pcre *\fIcode\fP, +.ti +5n +.B const char *\fIname\fP); +.PP +.br +.B int pcre_copy_named_substring(const pcre *\fIcode\fP, +.ti +5n +.B const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, const char *\fIstringname\fP, +.ti +5n +.B char *\fIbuffer\fP, int \fIbuffersize\fP); +.PP +.br +.B int pcre_get_named_substring(const pcre *\fIcode\fP, +.ti +5n +.B const char *\fIsubject\fP, int *\fIovector\fP, +.ti +5n +.B int \fIstringcount\fP, const char *\fIstringname\fP, +.ti +5n +.B const char **\fIstringptr\fP); +.PP +To extract a substring by name, you first have to find associated number. +For example, for this pattern +.sp + (a+)b(?<xxx>\ed+)... +.sp +the number of the subpattern called "xxx" is 2. You can find the number from +the name by calling \fBpcre_get_stringnumber()\fP. The first argument is the +compiled pattern, and the second is the name. The yield of the function is the +subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of +that name. +.P +Given the number, you can extract the substring directly, or use one of the +functions described in the previous section. For convenience, there are also +two functions that do the whole job. +.P +Most of the arguments of \fIpcre_copy_named_substring()\fP and +\fIpcre_get_named_substring()\fP are the same as those for the similarly named +functions that extract by number. As these are described in the previous +section, they are not re-described here. There are just two differences: +.P +First, instead of a substring number, a substring name is given. Second, there +is an extra argument, given at the start, which is a pointer to the compiled +pattern. This is needed in order to gain access to the name-to-number +translation table. +.P +These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they +then call \fIpcre_copy_substring()\fP or \fIpcre_get_substring()\fP, as +appropriate. +.P +.in 0 +Last updated: 09 September 2004 +.br +Copyright (c) 1997-2004 University of Cambridge. |