code/trunk/pcredemo.c

/*************************************************
*           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.

Compile thuswise:
  gcc -Wall pcredemo.c -I/usr/local/include -L/usr/local/lib \
    -R/usr/local/lib -lpcre

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.
*/


#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#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;
int erroffset;
int find_all;
int namecount;
int name_entry_size;
int ovector[OVECCOUNT];
int subject_length;
int rc, i;


/**************************************************************************
* 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\n");
  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\n", 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\n"); break;
    /*
    Handle other special cases if you like
    */
    default: printf("Matching error %d\n", rc); break;
    }
  pcre_free(re);     /* Release memory used for the compiled pattern */
  return 1;
  }

/* Match succeded */

printf("\nMatch succeeded at offset %d\n", ovector[0]);


/*************************************************************************
* We have found the first match within the subject string. If the output *
* vector wasn't big enough, set its size to the maximum. 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\n", 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\n", 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 *
* first shows 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\n"); else
  {
  unsigned char *tabptr;
  printf("Named substrings\n");

  /* 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\n", 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 and PCRE_ANCHORED flags set. The first  *
* of these tells PCRE that an empty string 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    *
* proceed round the loop.                                                *
*************************************************************************/

if (!find_all)
  {
  pcre_free(re);   /* Release the memory used for the compiled pattern */
  return 0;        /* Finish unless -g was given */
  }

/* 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 | 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, 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. */

  if (rc == PCRE_ERROR_NOMATCH)
    {
    if (options == 0) break;
    ovector[1] = start_offset + 1;
    continue;    /* Go round the loop again */
    }

  /* Other matching errors are not recoverable. */

  if (rc < 0)
    {
    printf("Matching error %d\n", rc);
    pcre_free(re);    /* Release memory used for the compiled pattern */
    return 1;
    }

  /* Match succeded */

  printf("\nMatch succeeded again at offset %d\n", 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\n", 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\n", i, substring_length, substring_start);
    }

  if (namecount <= 0) printf("No named substrings\n"); else
    {
    unsigned char *tabptr = name_table;
    printf("Named substrings\n");
    for (i = 0; i < namecount; i++)
      {
      int n = (tabptr[0] << 8) | tabptr[1];
      printf("(%d) %*s: %.*s\n", 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("\n");
pcre_free(re);       /* Release memory used for the compiled pattern */
return 0;
}

/* End of pcredemo.c */
1	/*************************************************
2	* PCRE DEMONSTRATION PROGRAM *
3	*************************************************/
4
5	/* This is a demonstration program to illustrate the most straightforward ways
6	of calling the PCRE regular expression library from a C program. See the
7	pcresample documentation for a short discussion.
8
9	Compile thuswise:
10	gcc -Wall pcredemo.c -I/usr/local/include -L/usr/local/lib \
11	-R/usr/local/lib -lpcre
12
13	Replace "/usr/local/include" and "/usr/local/lib" with wherever the include and
14	library files for PCRE are installed on your system. Only some operating
15	systems (e.g. Solaris) use the -R option.
16	*/
17
18
19	#ifdef HAVE_CONFIG_H
20	# include <config.h>
21	#endif
22
23	#include <stdio.h>
24	#include <string.h>
25	#include <pcre.h>
26
27	#define OVECCOUNT 30 /* should be a multiple of 3 */
28
29
30	int main(int argc, char **argv)
31	{
32	pcre *re;
33	const char *error;
34	char *pattern;
35	char *subject;
36	unsigned char *name_table;
37	int erroffset;
38	int find_all;
39	int namecount;
40	int name_entry_size;
41	int ovector[OVECCOUNT];
42	int subject_length;
43	int rc, i;
44
45
46	/**************************************************************************
47	* First, sort out the command line. There is only one possible option at *
48	* the moment, "-g" to request repeated matching to find all occurrences, *
49	* like Perl's /g option. We set the variable find_all to a non-zero value *
50	* if the -g option is present. Apart from that, there must be exactly two *
51	* arguments. *
52	**************************************************************************/
53
54	find_all = 0;
55	for (i = 1; i < argc; i++)
56	{
57	if (strcmp(argv[i], "-g") == 0) find_all = 1;
58	else break;
59	}
60
61	/* After the options, we require exactly two arguments, which are the pattern,
62	and the subject string. */
63
64	if (argc - i != 2)
65	{
66	printf("Two arguments required: a regex and a subject string\n");
67	return 1;
68	}
69
70	pattern = argv[i];
71	subject = argv[i+1];
72	subject_length = (int)strlen(subject);
73
74
75	/*************************************************************************
76	* Now we are going to compile the regular expression pattern, and handle *
77	* and errors that are detected. *
78	*************************************************************************/
79
80	re = pcre_compile(
81	pattern, /* the pattern */
82	0, /* default options */
83	&error, /* for error message */
84	&erroffset, /* for error offset */
85	NULL); /* use default character tables */
86
87	/* Compilation failed: print the error message and exit */
88
89	if (re == NULL)
90	{
91	printf("PCRE compilation failed at offset %d: %s\n", erroffset, error);
92	return 1;
93	}
94
95
96	/*************************************************************************
97	* If the compilation succeeded, we call PCRE again, in order to do a *
98	* pattern match against the subject string. This does just ONE match. If *
99	* further matching is needed, it will be done below. *
100	*************************************************************************/
101
102	rc = pcre_exec(
103	re, /* the compiled pattern */
104	NULL, /* no extra data - we didn't study the pattern */
105	subject, /* the subject string */
106	subject_length, /* the length of the subject */
107	0, /* start at offset 0 in the subject */
108	0, /* default options */
109	ovector, /* output vector for substring information */
110	OVECCOUNT); /* number of elements in the output vector */
111
112	/* Matching failed: handle error cases */
113
114	if (rc < 0)
115	{
116	switch(rc)
117	{
118	case PCRE_ERROR_NOMATCH: printf("No match\n"); break;
119	/*
120	Handle other special cases if you like
121	*/
122	default: printf("Matching error %d\n", rc); break;
123	}
124	pcre_free(re); /* Release memory used for the compiled pattern */
125	return 1;
126	}
127
128	/* Match succeded */
129
130	printf("\nMatch succeeded at offset %d\n", ovector[0]);
131
132
133	/*************************************************************************
134	* We have found the first match within the subject string. If the output *
135	* vector wasn't big enough, set its size to the maximum. Then output any *
136	* substrings that were captured. *
137	*************************************************************************/
138
139	/* The output vector wasn't big enough */
140
141	if (rc == 0)
142	{
143	rc = OVECCOUNT/3;
144	printf("ovector only has room for %d captured substrings\n", rc - 1);
145	}
146
147	/* Show substrings stored in the output vector by number. Obviously, in a real
148	application you might want to do things other than print them. */
149
150	for (i = 0; i < rc; i++)
151	{
152	char substring_start = subject + ovector[2i];
153	int substring_length = ovector[2i+1] - ovector[2i];
154	printf("%2d: %.*s\n", i, substring_length, substring_start);
155	}
156
157
158	/**************************************************************************
159	* That concludes the basic part of this demonstration program. We have *
160	* compiled a pattern, and performed a single match. The code that follows *
161	* first shows how to access named substrings, and then how to code for *
162	* repeated matches on the same subject. *
163	**************************************************************************/
164
165	/* See if there are any named substrings, and if so, show them by name. First
166	we have to extract the count of named parentheses from the pattern. */
167
168	(void)pcre_fullinfo(
169	re, /* the compiled pattern */
170	NULL, /* no extra data - we didn't study the pattern */
171	PCRE_INFO_NAMECOUNT, /* number of named substrings */
172	&namecount); /* where to put the answer */
173
174	if (namecount <= 0) printf("No named substrings\n"); else
175	{
176	unsigned char *tabptr;
177	printf("Named substrings\n");
178
179	/* Before we can access the substrings, we must extract the table for
180	translating names to numbers, and the size of each entry in the table. */
181
182	(void)pcre_fullinfo(
183	re, /* the compiled pattern */
184	NULL, /* no extra data - we didn't study the pattern */
185	PCRE_INFO_NAMETABLE, /* address of the table */
186	&name_table); /* where to put the answer */
187
188	(void)pcre_fullinfo(
189	re, /* the compiled pattern */
190	NULL, /* no extra data - we didn't study the pattern */
191	PCRE_INFO_NAMEENTRYSIZE, /* size of each entry in the table */
192	&name_entry_size); /* where to put the answer */
193
194	/* Now we can scan the table and, for each entry, print the number, the name,
195	and the substring itself. */
196
197	tabptr = name_table;
198	for (i = 0; i < namecount; i++)
199	{
200	int n = (tabptr[0] << 8) \| tabptr[1];
201	printf("(%d) %s: %.s\n", n, name_entry_size - 3, tabptr + 2,
202	ovector[2n+1] - ovector[2n], subject + ovector[2*n]);
203	tabptr += name_entry_size;
204	}
205	}
206
207
208	/*************************************************************************
209	* If the "-g" option was given on the command line, we want to continue *
210	* to search for additional matches in the subject string, in a similar *
211	* way to the /g option in Perl. This turns out to be trickier than you *
212	* might think because of the possibility of matching an empty string. *
213	* What happens is as follows: *
214	* *
215	* If the previous match was NOT for an empty string, we can just start *
216	* the next match at the end of the previous one. *
217	* *
218	* If the previous match WAS for an empty string, we can't do that, as it *
219	* would lead to an infinite loop. Instead, a special call of pcre_exec() *
220	* is made with the PCRE_NOTEMPTY and PCRE_ANCHORED flags set. The first *
221	* of these tells PCRE that an empty string is not a valid match; other *
222	* possibilities must be tried. The second flag restricts PCRE to one *
223	* match attempt at the initial string position. If this match succeeds, *
224	* an alternative to the empty string match has been found, and we can *
225	* proceed round the loop. *
226	*************************************************************************/
227
228	if (!find_all)
229	{
230	pcre_free(re); /* Release the memory used for the compiled pattern */
231	return 0; /* Finish unless -g was given */
232	}
233
234	/* Loop for second and subsequent matches */
235
236	for (;;)
237	{
238	int options = 0; /* Normally no options */
239	int start_offset = ovector[1]; /* Start at end of previous match */
240
241	/* If the previous match was for an empty string, we are finished if we are
242	at the end of the subject. Otherwise, arrange to run another match at the
243	same point to see if a non-empty match can be found. */
244
245	if (ovector[0] == ovector[1])
246	{
247	if (ovector[0] == subject_length) break;
248	options = PCRE_NOTEMPTY \| PCRE_ANCHORED;
249	}
250
251	/* Run the next matching operation */
252
253	rc = pcre_exec(
254	re, /* the compiled pattern */
255	NULL, /* no extra data - we didn't study the pattern */
256	subject, /* the subject string */
257	subject_length, /* the length of the subject */
258	start_offset, /* starting offset in the subject */
259	options, /* options */
260	ovector, /* output vector for substring information */
261	OVECCOUNT); /* number of elements in the output vector */
262
263	/* This time, a result of NOMATCH isn't an error. If the value in "options"
264	is zero, it just means we have found all possible matches, so the loop ends.
265	Otherwise, it means we have failed to find a non-empty-string match at a
266	point where there was a previous empty-string match. In this case, we do what
267	Perl does: advance the matching position by one, and continue. We do this by
268	setting the "end of previous match" offset, because that is picked up at the
269	top of the loop as the point at which to start again. */
270
271	if (rc == PCRE_ERROR_NOMATCH)
272	{
273	if (options == 0) break;
274	ovector[1] = start_offset + 1;
275	continue; /* Go round the loop again */
276	}
277
278	/* Other matching errors are not recoverable. */
279
280	if (rc < 0)
281	{
282	printf("Matching error %d\n", rc);
283	pcre_free(re); /* Release memory used for the compiled pattern */
284	return 1;
285	}
286
287	/* Match succeded */
288
289	printf("\nMatch succeeded again at offset %d\n", ovector[0]);
290
291	/* The match succeeded, but the output vector wasn't big enough. */
292
293	if (rc == 0)
294	{
295	rc = OVECCOUNT/3;
296	printf("ovector only has room for %d captured substrings\n", rc - 1);
297	}
298
299	/* As before, show substrings stored in the output vector by number, and then
300	also any named substrings. */
301
302	for (i = 0; i < rc; i++)
303	{
304	char substring_start = subject + ovector[2i];
305	int substring_length = ovector[2i+1] - ovector[2i];
306	printf("%2d: %.*s\n", i, substring_length, substring_start);
307	}
308
309	if (namecount <= 0) printf("No named substrings\n"); else
310	{
311	unsigned char *tabptr = name_table;
312	printf("Named substrings\n");
313	for (i = 0; i < namecount; i++)
314	{
315	int n = (tabptr[0] << 8) \| tabptr[1];
316	printf("(%d) %s: %.s\n", n, name_entry_size - 3, tabptr + 2,
317	ovector[2n+1] - ovector[2n], subject + ovector[2*n]);
318	tabptr += name_entry_size;
319	}
320	}
321	} /* End of loop to find second and subsequent matches */
322
323	printf("\n");
324	pcre_free(re); /* Release memory used for the compiled pattern */
325	return 0;
326	}
327
328	/* End of pcredemo.c */
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