#include <pcre2.h>
int pcre2_pattern_info(const pcre2_code *code, uint32_t what, void *where);
This function returns information about a compiled pattern. Its arguments are:
code Pointer to a compiled regular expression pattern
what What information is required
where Where to put the information
The recognized values for the what argument, and the information they request are as follows:
PCRE2_INFO_ALLOPTIONS Final options after compiling
PCRE2_INFO_ARGOPTIONS Options passed to pcre2_compile()
PCRE2_INFO_BACKREFMAX Number of highest backreference
PCRE2_INFO_BSR What \R matches:
PCRE2_BSR_UNICODE: Unicode line endings
PCRE2_BSR_ANYCRLF: CR, LF, or CRLF only
PCRE2_INFO_CAPTURECOUNT Number of capturing subpatterns
PCRE2_INFO_DEPTHLIMIT Backtracking depth limit if set,
otherwise PCRE2_ERROR_UNSET
PCRE2_INFO_EXTRAOPTIONS Extra options that were passed in the
compile context
PCRE2_INFO_FIRSTBITMAP Bitmap of first code units, or NULL
PCRE2_INFO_FIRSTCODETYPE Type of start-of-match information
0 nothing set
1 first code unit is set
2 start of string or after newline
PCRE2_INFO_FIRSTCODEUNIT First code unit when type is 1
PCRE2_INFO_FRAMESIZE Size of backtracking frame
PCRE2_INFO_HASBACKSLASHC Return 1 if pattern contains \C
PCRE2_INFO_HASCRORLF Return 1 if explicit CR or LF matches
exist in the pattern
PCRE2_INFO_HEAPLIMIT Heap memory limit if set,
otherwise PCRE2_ERROR_UNSET
PCRE2_INFO_JCHANGED Return 1 if (?J) or (?-J) was used
PCRE2_INFO_JITSIZE Size of JIT compiled code, or 0
PCRE2_INFO_LASTCODETYPE Type of must-be-present information
0 nothing set
1 code unit is set
PCRE2_INFO_LASTCODEUNIT Last code unit when type is 1
PCRE2_INFO_MATCHEMPTY 1 if the pattern can match an
empty string, 0 otherwise
PCRE2_INFO_MATCHLIMIT Match limit if set,
otherwise PCRE2_ERROR_UNSET
PCRE2_INFO_MAXLOOKBEHIND Length (in characters) of the longest
lookbehind assertion
PCRE2_INFO_MINLENGTH Lower bound length of matching strings
PCRE2_INFO_NAMECOUNT Number of named subpatterns
PCRE2_INFO_NAMEENTRYSIZE Size of name table entries
PCRE2_INFO_NAMETABLE Pointer to name table
PCRE2_CONFIG_NEWLINE Code for the newline sequence:
PCRE2_NEWLINE_CR
PCRE2_NEWLINE_LF
PCRE2_NEWLINE_CRLF
PCRE2_NEWLINE_ANY
PCRE2_NEWLINE_ANYCRLF
PCRE2_NEWLINE_NUL
PCRE2_INFO_RECURSIONLIMIT Obsolete synonym for PCRE2_INFO_DEPTHLIMIT
PCRE2_INFO_SIZE Size of compiled pattern
If where is NULL, the function returns the amount of memory needed for the requested information, in bytes. Otherwise, the where argument must point to an unsigned 32-bit integer (uint32_t variable), except for the following what values, when it must point to a variable of the type shown:
PCRE2_INFO_FIRSTBITMAP const uint8_t *
PCRE2_INFO_JITSIZE size_t
PCRE2_INFO_NAMETABLE PCRE2_SPTR
PCRE2_INFO_SIZE size_t
The yield of the function is zero on success or:
PCRE2_ERROR_NULL the argument code is NULL
PCRE2_ERROR_BADMAGIC the "magic number" was not found
PCRE2_ERROR_BADOPTION the value of what is invalid
PCRE2_ERROR_BADMODE the pattern was compiled in the wrong mode
PCRE2_ERROR_UNSET the requested information is not set
There is a complete description of the PCRE2 native API in the pcre2api page and a description of the POSIX API in the pcre2posix page.