| .TH PCRE2DEMO 3 " 4 June 2024" "PCRE2 10.43" |
| .\"AUTOMATICALLY GENERATED BY PrepareRelease - do not EDIT! |
| .SH NAME |
| PCRE2DEMO - A demonstration C program for PCRE2 |
| .SH "SOURCE CODE" |
| .rs |
| .sp |
| .\" Start example. |
| .de EX |
| . do ds mF \\n[.fam] |
| . nr mE \\n(.f |
| . nf |
| . nh |
| . do fam C |
| . ft CW |
| .. |
| . |
| . |
| .\" End example. |
| .de EE |
| . do fam \\*(mF |
| . ft \\n(mE |
| . fi |
| . hy \\n(HY |
| .. |
| . |
| .RS -7 |
| .EX |
| /************************************************* |
| * PCRE2 DEMONSTRATION PROGRAM * |
| *************************************************/ |
| |
| /* This is a demonstration program to illustrate a straightforward way of |
| using the PCRE2 regular expression library from a C program. See the |
| pcre2sample documentation for a short discussion ("man pcre2sample" if you have |
| the PCRE2 man pages installed). PCRE2 is a revised API for the library, and is |
| incompatible with the original PCRE API. |
| |
| There are actually three libraries, each supporting a different code unit |
| width. This demonstration program uses the 8-bit library. The default is to |
| process each code unit as a separate character, but if the pattern begins with |
| "(*UTF)", both it and the subject are treated as UTF-8 strings, where |
| characters may occupy multiple code units. |
| |
| In Unix-like environments, if PCRE2 is installed in your standard system |
| libraries, you should be able to compile this program using this command: |
| |
| cc -Wall pcre2demo.c -lpcre2-8 -o pcre2demo |
| |
| If PCRE2 is not installed in a standard place, it is likely to be installed |
| with support for the pkg-config mechanism. If you have pkg-config, you can |
| compile this program using this command: |
| |
| cc -Wall pcre2demo.c `pkg-config --cflags --libs libpcre2-8` -o pcre2demo |
| |
| If you do not have pkg-config, you may have to use something like this: |
| |
| cc -Wall pcre2demo.c -I/usr/local/include -L/usr/local/lib \e |
| -R/usr/local/lib -lpcre2-8 -o pcre2demo |
| |
| Replace "/usr/local/include" and "/usr/local/lib" with wherever the include and |
| library files for PCRE2 are installed on your system. Only some operating |
| systems (Solaris is one) use the -R option. |
| |
| Building under Windows: |
| |
| If you want to statically link this program against a non-dll .a file, you must |
| define PCRE2_STATIC before including pcre2.h, so in this environment, uncomment |
| the following line. */ |
| |
| /* #define PCRE2_STATIC */ |
| |
| /* The PCRE2_CODE_UNIT_WIDTH macro must be defined before including pcre2.h. |
| For a program that uses only one code unit width, setting it to 8, 16, or 32 |
| makes it possible to use generic function names such as pcre2_compile(). Note |
| that just changing 8 to 16 (for example) is not sufficient to convert this |
| program to process 16-bit characters. Even in a fully 16-bit environment, where |
| string-handling functions such as strcmp() and printf() work with 16-bit |
| characters, the code for handling the table of named substrings will still need |
| to be modified. */ |
| |
| #define PCRE2_CODE_UNIT_WIDTH 8 |
| |
| #include <stdio.h> |
| #include <string.h> |
| #include <pcre2.h> |
| |
| |
| /************************************************************************** |
| * Here is the program. The API includes the concept of "contexts" for * |
| * setting up unusual interface requirements for compiling and matching, * |
| * such as custom memory managers and non-standard newline definitions. * |
| * This program does not do any of this, so it makes no use of contexts, * |
| * always passing NULL where a context could be given. * |
| **************************************************************************/ |
| |
| int main(int argc, char **argv) |
| { |
| pcre2_code *re; |
| PCRE2_SPTR pattern; /* PCRE2_SPTR is a pointer to unsigned code units of */ |
| PCRE2_SPTR subject; /* the appropriate width (in this case, 8 bits). */ |
| PCRE2_SPTR name_table; |
| |
| int crlf_is_newline; |
| int errornumber; |
| int find_all; |
| int i; |
| int rc; |
| int utf8; |
| |
| uint32_t option_bits; |
| uint32_t namecount; |
| uint32_t name_entry_size; |
| uint32_t newline; |
| |
| PCRE2_SIZE erroroffset; |
| PCRE2_SIZE *ovector; |
| PCRE2_SIZE subject_length; |
| |
| pcre2_match_data *match_data; |
| |
| |
| /************************************************************************** |
| * First, sort out the command line. There is only one possible option at * |
| * the moment, "-g" to request repeated matching to find all occurrences, * |
| * like Perl's /g option. We set the variable find_all to a non-zero value * |
| * if the -g option is present. * |
| **************************************************************************/ |
| |
| find_all = 0; |
| for (i = 1; i < argc; i++) |
| { |
| if (strcmp(argv[i], "-g") == 0) find_all = 1; |
| else if (argv[i][0] == '-') |
| { |
| printf("Unrecognised option %s\en", argv[i]); |
| return 1; |
| } |
| else break; |
| } |
| |
| /* After the options, we require exactly two arguments, which are the pattern, |
| and the subject string. */ |
| |
| if (argc - i != 2) |
| { |
| printf("Exactly two arguments required: a regex and a subject string\en"); |
| return 1; |
| } |
| |
| /* Pattern and subject are char arguments, so they can be straightforwardly |
| cast to PCRE2_SPTR because we are working in 8-bit code units. The subject |
| length is cast to PCRE2_SIZE for completeness, though PCRE2_SIZE is in fact |
| defined to be size_t. */ |
| |
| pattern = (PCRE2_SPTR)argv[i]; |
| subject = (PCRE2_SPTR)argv[i+1]; |
| subject_length = (PCRE2_SIZE)strlen((char *)subject); |
| |
| |
| /************************************************************************* |
| * Now we are going to compile the regular expression pattern, and handle * |
| * any errors that are detected. * |
| *************************************************************************/ |
| |
| re = pcre2_compile( |
| pattern, /* the pattern */ |
| PCRE2_ZERO_TERMINATED, /* indicates pattern is zero-terminated */ |
| 0, /* default options */ |
| &errornumber, /* for error number */ |
| &erroroffset, /* for error offset */ |
| NULL); /* use default compile context */ |
| |
| /* Compilation failed: print the error message and exit. */ |
| |
| if (re == NULL) |
| { |
| PCRE2_UCHAR buffer[256]; |
| pcre2_get_error_message(errornumber, buffer, sizeof(buffer)); |
| printf("PCRE2 compilation failed at offset %d: %s\en", (int)erroroffset, |
| buffer); |
| return 1; |
| } |
| |
| |
| /************************************************************************* |
| * If the compilation succeeded, we call PCRE2 again, in order to do a * |
| * pattern match against the subject string. This does just ONE match. If * |
| * further matching is needed, it will be done below. Before running the * |
| * match we must set up a match_data block for holding the result. Using * |
| * pcre2_match_data_create_from_pattern() ensures that the block is * |
| * exactly the right size for the number of capturing parentheses in the * |
| * pattern. If you need to know the actual size of a match_data block as * |
| * a number of bytes, you can find it like this: * |
| * * |
| * PCRE2_SIZE match_data_size = pcre2_get_match_data_size(match_data); * |
| *************************************************************************/ |
| |
| match_data = pcre2_match_data_create_from_pattern(re, NULL); |
| |
| /* Now run the match. */ |
| |
| rc = pcre2_match( |
| re, /* the compiled pattern */ |
| subject, /* the subject string */ |
| subject_length, /* the length of the subject */ |
| 0, /* start at offset 0 in the subject */ |
| 0, /* default options */ |
| match_data, /* block for storing the result */ |
| NULL); /* use default match context */ |
| |
| /* Matching failed: handle error cases */ |
| |
| if (rc < 0) |
| { |
| switch(rc) |
| { |
| case PCRE2_ERROR_NOMATCH: printf("No match\en"); break; |
| /* |
| Handle other special cases if you like |
| */ |
| default: printf("Matching error %d\en", rc); break; |
| } |
| pcre2_match_data_free(match_data); /* Release memory used for the match */ |
| pcre2_code_free(re); /* data and the compiled pattern. */ |
| return 1; |
| } |
| |
| /* Match succeeded. Get a pointer to the output vector, where string offsets |
| are stored. */ |
| |
| ovector = pcre2_get_ovector_pointer(match_data); |
| printf("Match succeeded at offset %d\en", (int)ovector[0]); |
| |
| |
| /************************************************************************* |
| * We have found the first match within the subject string. If the output * |
| * vector wasn't big enough, say so. Then output any substrings that were * |
| * captured. * |
| *************************************************************************/ |
| |
| /* The output vector wasn't big enough. This should not happen, because we used |
| pcre2_match_data_create_from_pattern() above. */ |
| |
| if (rc == 0) |
| printf("ovector was not big enough for all the captured substrings\en"); |
| |
| /* Since release 10.38 PCRE2 has locked out the use of \eK in lookaround |
| assertions. However, there is an option to re-enable the old behaviour. If that |
| is set, it is possible to run patterns such as /(?=.\eK)/ that use \eK in an |
| assertion to set the start of a match later than its end. In this demonstration |
| program, we show how to detect this case, but it shouldn't arise because the |
| option is never set. */ |
| |
| if (ovector[0] > ovector[1]) |
| { |
| printf("\e\eK was used in an assertion to set the match start after its end.\en" |
| "From end to start the match was: %.*s\en", (int)(ovector[0] - ovector[1]), |
| (char *)(subject + ovector[1])); |
| printf("Run abandoned\en"); |
| pcre2_match_data_free(match_data); |
| pcre2_code_free(re); |
| return 1; |
| } |
| |
| /* Show substrings stored in the output vector by number. Obviously, in a real |
| application you might want to do things other than print them. */ |
| |
| for (i = 0; i < rc; i++) |
| { |
| PCRE2_SPTR substring_start = subject + ovector[2*i]; |
| PCRE2_SIZE substring_length = ovector[2*i+1] - ovector[2*i]; |
| printf("%2d: %.*s\en", i, (int)substring_length, (char *)substring_start); |
| } |
| |
| |
| /************************************************************************** |
| * That concludes the basic part of this demonstration program. We have * |
| * compiled a pattern, and performed a single match. The code that follows * |
| * shows first how to access named substrings, and then how to code for * |
| * repeated matches on the same subject. * |
| **************************************************************************/ |
| |
| /* See if there are any named substrings, and if so, show them by name. First |
| we have to extract the count of named parentheses from the pattern. */ |
| |
| (void)pcre2_pattern_info( |
| re, /* the compiled pattern */ |
| PCRE2_INFO_NAMECOUNT, /* get the number of named substrings */ |
| &namecount); /* where to put the answer */ |
| |
| if (namecount == 0) printf("No named substrings\en"); else |
| { |
| PCRE2_SPTR tabptr; |
| printf("Named substrings\en"); |
| |
| /* Before we can access the substrings, we must extract the table for |
| translating names to numbers, and the size of each entry in the table. */ |
| |
| (void)pcre2_pattern_info( |
| re, /* the compiled pattern */ |
| PCRE2_INFO_NAMETABLE, /* address of the table */ |
| &name_table); /* where to put the answer */ |
| |
| (void)pcre2_pattern_info( |
| re, /* the compiled pattern */ |
| PCRE2_INFO_NAMEENTRYSIZE, /* size of each entry in the table */ |
| &name_entry_size); /* where to put the answer */ |
| |
| /* Now we can scan the table and, for each entry, print the number, the name, |
| and the substring itself. In the 8-bit library the number is held in two |
| bytes, most significant first. */ |
| |
| tabptr = name_table; |
| for (i = 0; i < namecount; i++) |
| { |
| int n = (tabptr[0] << 8) | tabptr[1]; |
| printf("(%d) %*s: %.*s\en", n, name_entry_size - 3, tabptr + 2, |
| (int)(ovector[2*n+1] - ovector[2*n]), subject + ovector[2*n]); |
| tabptr += name_entry_size; |
| } |
| } |
| |
| |
| /************************************************************************* |
| * If the "-g" option was given on the command line, we want to continue * |
| * to search for additional matches in the subject string, in a similar * |
| * way to the /g option in Perl. This turns out to be trickier than you * |
| * might think because of the possibility of matching an empty string. * |
| * What happens is as follows: * |
| * * |
| * If the previous match was NOT for an empty string, we can just start * |
| * the next match at the end of the previous one. * |
| * * |
| * If the previous match WAS for an empty string, we can't do that, as it * |
| * would lead to an infinite loop. Instead, a call of pcre2_match() is * |
| * made with the PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED flags set. The * |
| * first of these tells PCRE2 that an empty string at the start of the * |
| * subject is not a valid match; other possibilities must be tried. The * |
| * second flag restricts PCRE2 to one match attempt at the initial string * |
| * position. If this match succeeds, an alternative to the empty string * |
| * match has been found, and we can print it and proceed round the loop, * |
| * advancing by the length of whatever was found. If this match does not * |
| * succeed, we still stay in the loop, advancing by just one character. * |
| * In UTF-8 mode, which can be set by (*UTF) in the pattern, this may be * |
| * more than one byte. * |
| * * |
| * However, there is a complication concerned with newlines. When the * |
| * newline convention is such that CRLF is a valid newline, we must * |
| * advance by two characters rather than one. The newline convention can * |
| * be set in the regex by (*CR), etc.; if not, we must find the default. * |
| *************************************************************************/ |
| |
| if (!find_all) /* Check for -g */ |
| { |
| pcre2_match_data_free(match_data); /* Release the memory that was used */ |
| pcre2_code_free(re); /* for the match data and the pattern. */ |
| return 0; /* Exit the program. */ |
| } |
| |
| /* Before running the loop, check for UTF-8 and whether CRLF is a valid newline |
| sequence. First, find the options with which the regex was compiled and extract |
| the UTF state. */ |
| |
| (void)pcre2_pattern_info(re, PCRE2_INFO_ALLOPTIONS, &option_bits); |
| utf8 = (option_bits & PCRE2_UTF) != 0; |
| |
| /* Now find the newline convention and see whether CRLF is a valid newline |
| sequence. */ |
| |
| (void)pcre2_pattern_info(re, PCRE2_INFO_NEWLINE, &newline); |
| crlf_is_newline = newline == PCRE2_NEWLINE_ANY || |
| newline == PCRE2_NEWLINE_CRLF || |
| newline == PCRE2_NEWLINE_ANYCRLF; |
| |
| /* Loop for second and subsequent matches */ |
| |
| for (;;) |
| { |
| uint32_t options = 0; /* Normally no options */ |
| PCRE2_SIZE start_offset = ovector[1]; /* Start at end of previous match */ |
| |
| /* If the previous match was for an empty string, we are finished if we are |
| at the end of the subject. Otherwise, arrange to run another match at the |
| same point to see if a non-empty match can be found. */ |
| |
| if (ovector[0] == ovector[1]) |
| { |
| if (ovector[0] == subject_length) break; |
| options = PCRE2_NOTEMPTY_ATSTART | PCRE2_ANCHORED; |
| } |
| |
| /* If the previous match was not an empty string, there is one tricky case to |
| consider. If a pattern contains \eK within a lookbehind assertion at the |
| start, the end of the matched string can be at the offset where the match |
| started. Without special action, this leads to a loop that keeps on matching |
| the same substring. We must detect this case and arrange to move the start on |
| by one character. The pcre2_get_startchar() function returns the starting |
| offset that was passed to pcre2_match(). */ |
| |
| else |
| { |
| PCRE2_SIZE startchar = pcre2_get_startchar(match_data); |
| if (start_offset <= startchar) |
| { |
| if (startchar >= subject_length) break; /* Reached end of subject. */ |
| start_offset = startchar + 1; /* Advance by one character. */ |
| if (utf8) /* If UTF-8, it may be more */ |
| { /* than one code unit. */ |
| for (; start_offset < subject_length; start_offset++) |
| if ((subject[start_offset] & 0xc0) != 0x80) break; |
| } |
| } |
| } |
| |
| /* Run the next matching operation */ |
| |
| rc = pcre2_match( |
| re, /* the compiled pattern */ |
| subject, /* the subject string */ |
| subject_length, /* the length of the subject */ |
| start_offset, /* starting offset in the subject */ |
| options, /* options */ |
| match_data, /* block for storing the result */ |
| NULL); /* use default match context */ |
| |
| /* This time, a result of NOMATCH isn't an error. If the value in "options" |
| is zero, it just means we have found all possible matches, so the loop ends. |
| Otherwise, it means we have failed to find a non-empty-string match at a |
| point where there was a previous empty-string match. In this case, we do what |
| Perl does: advance the matching position by one character, and continue. We |
| do this by setting the "end of previous match" offset, because that is picked |
| up at the top of the loop as the point at which to start again. |
| |
| There are two complications: (a) When CRLF is a valid newline sequence, and |
| the current position is just before it, advance by an extra byte. (b) |
| Otherwise we must ensure that we skip an entire UTF character if we are in |
| UTF mode. */ |
| |
| if (rc == PCRE2_ERROR_NOMATCH) |
| { |
| if (options == 0) break; /* All matches found */ |
| ovector[1] = start_offset + 1; /* Advance one code unit */ |
| if (crlf_is_newline && /* If CRLF is a newline & */ |
| start_offset < subject_length - 1 && /* we are at CRLF, */ |
| subject[start_offset] == '\er' && |
| subject[start_offset + 1] == '\en') |
| ovector[1] += 1; /* Advance by one more. */ |
| else if (utf8) /* Otherwise, ensure we */ |
| { /* advance a whole UTF-8 */ |
| while (ovector[1] < subject_length) /* character. */ |
| { |
| if ((subject[ovector[1]] & 0xc0) != 0x80) break; |
| ovector[1] += 1; |
| } |
| } |
| continue; /* Go round the loop again */ |
| } |
| |
| /* Other matching errors are not recoverable. */ |
| |
| if (rc < 0) |
| { |
| printf("Matching error %d\en", rc); |
| pcre2_match_data_free(match_data); |
| pcre2_code_free(re); |
| return 1; |
| } |
| |
| /* Match succeeded */ |
| |
| printf("\enMatch succeeded again at offset %d\en", (int)ovector[0]); |
| |
| /* The match succeeded, but the output vector wasn't big enough. This |
| should not happen. */ |
| |
| if (rc == 0) |
| printf("ovector was not big enough for all the captured substrings\en"); |
| |
| /* We must guard against patterns such as /(?=.\eK)/ that use \eK in an |
| assertion to set the start of a match later than its end. In this |
| demonstration program, we just detect this case and give up. */ |
| |
| if (ovector[0] > ovector[1]) |
| { |
| printf("\e\eK was used in an assertion to set the match start after its end.\en" |
| "From end to start the match was: %.*s\en", (int)(ovector[0] - ovector[1]), |
| (char *)(subject + ovector[1])); |
| printf("Run abandoned\en"); |
| pcre2_match_data_free(match_data); |
| pcre2_code_free(re); |
| return 1; |
| } |
| |
| /* As before, show substrings stored in the output vector by number, and then |
| also any named substrings. */ |
| |
| for (i = 0; i < rc; i++) |
| { |
| PCRE2_SPTR substring_start = subject + ovector[2*i]; |
| size_t substring_length = ovector[2*i+1] - ovector[2*i]; |
| printf("%2d: %.*s\en", i, (int)substring_length, (char *)substring_start); |
| } |
| |
| if (namecount == 0) printf("No named substrings\en"); else |
| { |
| PCRE2_SPTR tabptr = name_table; |
| printf("Named substrings\en"); |
| for (i = 0; i < namecount; i++) |
| { |
| int n = (tabptr[0] << 8) | tabptr[1]; |
| printf("(%d) %*s: %.*s\en", n, name_entry_size - 3, tabptr + 2, |
| (int)(ovector[2*n+1] - ovector[2*n]), subject + ovector[2*n]); |
| tabptr += name_entry_size; |
| } |
| } |
| } /* End of loop to find second and subsequent matches */ |
| |
| printf("\en"); |
| pcre2_match_data_free(match_data); |
| pcre2_code_free(re); |
| return 0; |
| } |
| |
| /* End of pcre2demo.c */ |
| .EE |
