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+.\" Start example.
+.de EX
+. nr mE \\n(.f
+. nf
+. nh
+. ft CW
+..
+.
+.
+.\" End example.
+.de EE
+. ft \\n(mE
+. fi
+. hy \\n(HY
+..
+.
+.EX
+/*************************************************
+* PCRE DEMONSTRATION PROGRAM *
+*************************************************/
+
+/* This is a demonstration program to illustrate the most straightforward ways
+of calling the PCRE regular expression library from a C program. See the
+pcresample documentation for a short discussion ("man pcresample" if you have
+the PCRE man pages installed).
+
+In Unix-like environments, if PCRE is installed in your standard system
+libraries, you should be able to compile this program using this command:
+
+gcc -Wall pcredemo.c -lpcre -o pcredemo
+
+If PCRE 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:
+
+gcc -Wall pcredemo.c `pkg-config --cflags --libs libpcre` -o pcredemo
+
+If you do not have pkg-config, you may have to use this:
+
+gcc -Wall pcredemo.c -I/usr/local/include -L/usr/local/lib \e
+ -R/usr/local/lib -lpcre -o pcredemo
+
+Replace "/usr/local/include" and "/usr/local/lib" with wherever the include and
+library files for PCRE are installed on your system. Only some operating
+systems (e.g. Solaris) use the -R option.
+
+Building under Windows:
+
+If you want to statically link this program against a non-dll .a file, you must
+define PCRE_STATIC before including pcre.h, otherwise the pcre_malloc() and
+pcre_free() exported functions will be declared __declspec(dllimport), with
+unwanted results. So in this environment, uncomment the following line. */
+
+/* #define PCRE_STATIC */
+
+#include <stdio.h>
+#include <string.h>
+#include <pcre.h>
+
+#define OVECCOUNT 30 /* should be a multiple of 3 */
+
+
+int main(int argc, char **argv)
+{
+pcre *re;
+const char *error;
+char *pattern;
+char *subject;
+unsigned char *name_table;
+unsigned int option_bits;
+int erroffset;
+int find_all;
+int crlf_is_newline;
+int namecount;
+int name_entry_size;
+int ovector[OVECCOUNT];
+int subject_length;
+int rc, i;
+int utf8;
+
+
+/**************************************************************************
+* 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. Apart from that, there must be exactly two *
+* arguments. *
+**************************************************************************/
+
+find_all = 0;
+for (i = 1; i < argc; i++)
+ {
+ if (strcmp(argv[i], "-g") == 0) find_all = 1;
+ else break;
+ }
+
+/* After the options, we require exactly two arguments, which are the pattern,
+and the subject string. */
+
+if (argc - i != 2)
+ {
+ printf("Two arguments required: a regex and a subject string\en");
+ return 1;
+ }
+
+pattern = argv[i];
+subject = argv[i+1];
+subject_length = (int)strlen(subject);
+
+
+/*************************************************************************
+* Now we are going to compile the regular expression pattern, and handle *
+* and errors that are detected. *
+*************************************************************************/
+
+re = pcre_compile(
+ pattern, /* the pattern */
+ 0, /* default options */
+ &error, /* for error message */
+ &erroffset, /* for error offset */
+ NULL); /* use default character tables */
+
+/* Compilation failed: print the error message and exit */
+
+if (re == NULL)
+ {
+ printf("PCRE compilation failed at offset %d: %s\en", erroffset, error);
+ return 1;
+ }
+
+
+/*************************************************************************
+* If the compilation succeeded, we call PCRE 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. *
+*************************************************************************/
+
+rc = pcre_exec(
+ re, /* the compiled pattern */
+ NULL, /* no extra data - we didn't study the pattern */
+ subject, /* the subject string */
+ subject_length, /* the length of the subject */
+ 0, /* start at offset 0 in the subject */
+ 0, /* default options */
+ ovector, /* output vector for substring information */
+ OVECCOUNT); /* number of elements in the output vector */
+
+/* Matching failed: handle error cases */
+
+if (rc < 0)
+ {
+ switch(rc)
+ {
+ case PCRE_ERROR_NOMATCH: printf("No match\en"); break;
+ /*
+ Handle other special cases if you like
+ */
+ default: printf("Matching error %d\en", rc); break;
+ }
+ pcre_free(re); /* Release memory used for the compiled pattern */
+ return 1;
+ }
+
+/* Match succeded */
+
+printf("\enMatch succeeded at offset %d\en", 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 */
+
+if (rc == 0)
+ {
+ rc = OVECCOUNT/3;
+ printf("ovector only has room for %d captured substrings\en", rc - 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++)
+ {
+ char *substring_start = subject + ovector[2*i];
+ int substring_length = ovector[2*i+1] - ovector[2*i];
+ printf("%2d: %.*s\en", i, substring_length, 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)pcre_fullinfo(
+ re, /* the compiled pattern */
+ NULL, /* no extra data - we didn't study the pattern */
+ PCRE_INFO_NAMECOUNT, /* number of named substrings */
+ &namecount); /* where to put the answer */
+
+if (namecount <= 0) printf("No named substrings\en"); else
+ {
+ unsigned char *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)pcre_fullinfo(
+ re, /* the compiled pattern */
+ NULL, /* no extra data - we didn't study the pattern */
+ PCRE_INFO_NAMETABLE, /* address of the table */
+ &name_table); /* where to put the answer */
+
+ (void)pcre_fullinfo(
+ re, /* the compiled pattern */
+ NULL, /* no extra data - we didn't study the pattern */
+ PCRE_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. */
+
+ 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,
+ 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 special call of pcre_exec() *
+* is made with the PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED flags set. *
+* The first of these tells PCRE that an empty string at the start of the *
+* subject is not a valid match; other possibilities must be tried. The *
+* second flag restricts PCRE 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 (*UTF8) 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 */
+ {
+ pcre_free(re); /* Release the memory used for the compiled pattern */
+ return 0; /* Finish unless -g was given */
+ }
+
+/* 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; extract
+the UTF-8 state, and mask off all but the newline options. */
+
+(void)pcre_fullinfo(re, NULL, PCRE_INFO_OPTIONS, &option_bits);
+utf8 = option_bits & PCRE_UTF8;
+option_bits &= PCRE_NEWLINE_CR|PCRE_NEWLINE_LF|PCRE_NEWLINE_CRLF|
+ PCRE_NEWLINE_ANY|PCRE_NEWLINE_ANYCRLF;
+
+/* If no newline options were set, find the default newline convention from the
+build configuration. */
+
+if (option_bits == 0)
+ {
+ int d;
+ (void)pcre_config(PCRE_CONFIG_NEWLINE, &d);
+ /* Note that these values are always the ASCII ones, even in
+ EBCDIC environments. CR = 13, NL = 10. */
+ option_bits = (d == 13)? PCRE_NEWLINE_CR :
+ (d == 10)? PCRE_NEWLINE_LF :
+ (d == (13<<8 | 10))? PCRE_NEWLINE_CRLF :
+ (d == -2)? PCRE_NEWLINE_ANYCRLF :
+ (d == -1)? PCRE_NEWLINE_ANY : 0;
+ }
+
+/* See if CRLF is a valid newline sequence. */
+
+crlf_is_newline =
+ option_bits == PCRE_NEWLINE_ANY ||
+ option_bits == PCRE_NEWLINE_CRLF ||
+ option_bits == PCRE_NEWLINE_ANYCRLF;
+
+/* Loop for second and subsequent matches */
+
+for (;;)
+ {
+ int options = 0; /* Normally no options */
+ int 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 = PCRE_NOTEMPTY_ATSTART | PCRE_ANCHORED;
+ }
+
+ /* Run the next matching operation */
+
+ rc = pcre_exec(
+ re, /* the compiled pattern */
+ NULL, /* no extra data - we didn't study the pattern */
+ subject, /* the subject string */
+ subject_length, /* the length of the subject */
+ start_offset, /* starting offset in the subject */
+ options, /* options */
+ ovector, /* output vector for substring information */
+ OVECCOUNT); /* number of elements in the output vector */
+
+ /* 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-8 character if we are in
+ UTF-8 mode. */
+
+ if (rc == PCRE_ERROR_NOMATCH)
+ {
+ if (options == 0) break; /* All matches found */
+ ovector[1] = start_offset + 1; /* Advance one byte */
+ if (crlf_is_newline && /* If CRLF is 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);
+ pcre_free(re); /* Release memory used for the compiled pattern */
+ return 1;
+ }
+
+ /* Match succeded */
+
+ printf("\enMatch succeeded again at offset %d\en", ovector[0]);
+
+ /* The match succeeded, but the output vector wasn't big enough. */
+
+ if (rc == 0)
+ {
+ rc = OVECCOUNT/3;
+ printf("ovector only has room for %d captured substrings\en", rc - 1);
+ }
+
+ /* As before, show substrings stored in the output vector by number, and then
+ also any named substrings. */
+
+ for (i = 0; i < rc; i++)
+ {
+ char *substring_start = subject + ovector[2*i];
+ int substring_length = ovector[2*i+1] - ovector[2*i];
+ printf("%2d: %.*s\en", i, substring_length, substring_start);
+ }
+
+ if (namecount <= 0) printf("No named substrings\en"); else
+ {
+ unsigned char *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,
+ 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");
+pcre_free(re); /* Release memory used for the compiled pattern */
+return 0;
+}
+
+/* End of pcredemo.c */
+.EE