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1  .TH PCRE 3  .TH PCREBUILD 3
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
4  .SH PCRE BUILD-TIME OPTIONS  .SH "PCRE BUILD-TIME OPTIONS"
5  .rs  .rs
6  .sp  .sp
7  This document describes the optional features of PCRE that can be selected when  This document describes the optional features of PCRE that can be selected when
8  the library is compiled. They are all selected, or deselected, by providing  the library is compiled. It assumes use of the \fBconfigure\fP script, where
9  options to the \fBconfigure\fR script which is run before the \fBmake\fR  the optional features are selected or deselected by providing options to
10  command. The complete list of options for \fBconfigure\fR (which includes the  \fBconfigure\fP before running the \fBmake\fP command. However, the same
11  standard ones such as the selection of the installation directory) can be  options can be selected in both Unix-like and non-Unix-like environments using
12  obtained by running  the GUI facility of \fBCMakeSetup\fP if you are using \fBCMake\fP instead of
13    \fBconfigure\fP to build PCRE.
14    .P
15    The complete list of options for \fBconfigure\fP (which includes the standard
16    ones such as the selection of the installation directory) can be obtained by
17    running
18    .sp
19    ./configure --help    ./configure --help
20    .sp
21  The following sections describe certain options whose names begin with --enable  The following sections include descriptions of options whose names begin with
22  or --disable. These settings specify changes to the defaults for the  --enable or --disable. These settings specify changes to the defaults for the
23  \fBconfigure\fR command. Because of the way that \fBconfigure\fR works,  \fBconfigure\fP command. Because of the way that \fBconfigure\fP works,
24  --enable and --disable always come in pairs, so the complementary option always  --enable and --disable always come in pairs, so the complementary option always
25  exists as well, but as it specifies the default, it is not described.  exists as well, but as it specifies the default, it is not described.
26    .
27  .SH UTF-8 SUPPORT  .SH "C++ SUPPORT"
28    .rs
29    .sp
30    By default, the \fBconfigure\fP script will search for a C++ compiler and C++
31    header files. If it finds them, it automatically builds the C++ wrapper library
32    for PCRE. You can disable this by adding
33    .sp
34      --disable-cpp
35    .sp
36    to the \fBconfigure\fP command.
37    .
38    .SH "UTF-8 SUPPORT"
39  .rs  .rs
40  .sp  .sp
41  To build PCRE with support for UTF-8 character strings, add  To build PCRE with support for UTF-8 character strings, add
42    .sp
43    --enable-utf8    --enable-utf8
44    .sp
45  to the \fBconfigure\fR command. Of itself, this does not make PCRE treat  to the \fBconfigure\fP command. Of itself, this does not make PCRE treat
46  strings as UTF-8. As well as compiling PCRE with this option, you also have  strings as UTF-8. As well as compiling PCRE with this option, you also have
47  have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fR  have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fP
48  function.  function.
49    .
50  .SH CODE VALUE OF NEWLINE  .SH "UNICODE CHARACTER PROPERTY SUPPORT"
51    .rs
52    .sp
53    UTF-8 support allows PCRE to process character values greater than 255 in the
54    strings that it handles. On its own, however, it does not provide any
55    facilities for accessing the properties of such characters. If you want to be
56    able to use the pattern escapes \eP, \ep, and \eX, which refer to Unicode
57    character properties, you must add
58    .sp
59      --enable-unicode-properties
60    .sp
61    to the \fBconfigure\fP command. This implies UTF-8 support, even if you have
62    not explicitly requested it.
63    .P
64    Including Unicode property support adds around 30K of tables to the PCRE
65    library. Only the general category properties such as \fILu\fP and \fINd\fP are
66    supported. Details are given in the
67    .\" HREF
68    \fBpcrepattern\fP
69    .\"
70    documentation.
71    .
72    .SH "CODE VALUE OF NEWLINE"
73  .rs  .rs
74  .sp  .sp
75  By default, PCRE treats character 10 (linefeed) as the newline character. This  By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
76  is the normal newline character on Unix-like systems. You can compile PCRE to  of a line. This is the normal newline character on Unix-like systems. You can
77  use character 13 (carriage return) instead by adding  compile PCRE to use character 13 (carriage return, CR) instead, by adding
78    .sp
79    --enable-newline-is-cr    --enable-newline-is-cr
80    .sp
81  to the \fBconfigure\fR command. For completeness there is also a  to the \fBconfigure\fP command. There is also a --enable-newline-is-lf option,
82  --enable-newline-is-lf option, which explicitly specifies linefeed as the  which explicitly specifies linefeed as the newline character.
83  newline character.  .sp
84    Alternatively, you can specify that line endings are to be indicated by the two
85  .SH BUILDING SHARED AND STATIC LIBRARIES  character sequence CRLF. If you want this, add
86    .sp
87      --enable-newline-is-crlf
88    .sp
89    to the \fBconfigure\fP command. There is a fourth option, specified by
90    .sp
91      --enable-newline-is-anycrlf
92    .sp
93    which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
94    indicating a line ending. Finally, a fifth option, specified by
95    .sp
96      --enable-newline-is-any
97    .sp
98    causes PCRE to recognize any Unicode newline sequence.
99    .P
100    Whatever line ending convention is selected when PCRE is built can be
101    overridden when the library functions are called. At build time it is
102    conventional to use the standard for your operating system.
103    .
104    .SH "WHAT \eR MATCHES"
105  .rs  .rs
106  .sp  .sp
107  The PCRE building process uses \fBlibtool\fR to build both shared and static  By default, the sequence \eR in a pattern matches any Unicode newline sequence,
108    whatever has been selected as the line ending sequence. If you specify
109    .sp
110      --enable-bsr-anycrlf
111    .sp
112    the default is changed so that \eR matches only CR, LF, or CRLF. Whatever is
113    selected when PCRE is built can be overridden when the library functions are
114    called.
115    .
116    .SH "BUILDING SHARED AND STATIC LIBRARIES"
117    .rs
118    .sp
119    The PCRE building process uses \fBlibtool\fP to build both shared and static
120  Unix libraries by default. You can suppress one of these by adding one of  Unix libraries by default. You can suppress one of these by adding one of
121    .sp
122    --disable-shared    --disable-shared
123    --disable-static    --disable-static
124    .sp
125  to the \fBconfigure\fR command, as required.  to the \fBconfigure\fP command, as required.
126    .
127  .SH POSIX MALLOC USAGE  .SH "POSIX MALLOC USAGE"
128  .rs  .rs
129  .sp  .sp
130  When PCRE is called through the POSIX interface (see the \fBpcreposix\fR  When PCRE is called through the POSIX interface (see the
131    .\" HREF
132    \fBpcreposix\fP
133    .\"
134  documentation), additional working storage is required for holding the pointers  documentation), additional working storage is required for holding the pointers
135  to capturing substrings because PCRE requires three integers per substring,  to capturing substrings, because PCRE requires three integers per substring,
136  whereas the POSIX interface provides only two. If the number of expected  whereas the POSIX interface provides only two. If the number of expected
137  substrings is small, the wrapper function uses space on the stack, because this  substrings is small, the wrapper function uses space on the stack, because this
138  is faster than using \fBmalloc()\fR for each call. The default threshold above  is faster than using \fBmalloc()\fP for each call. The default threshold above
139  which the stack is no longer used is 10; it can be changed by adding a setting  which the stack is no longer used is 10; it can be changed by adding a setting
140  such as  such as
141    .sp
142    --with-posix-malloc-threshold=20    --with-posix-malloc-threshold=20
   
 to the \fBconfigure\fR command.  
   
 .SH LIMITING PCRE RESOURCE USAGE  
 .rs  
143  .sp  .sp
144  Internally, PCRE has a function called \fBmatch()\fR which it calls repeatedly  to the \fBconfigure\fP command.
145  (possibly recursively) when performing a matching operation. By limiting the  .
146  number of times this function may be called, a limit can be placed on the  .SH "HANDLING VERY LARGE PATTERNS"
 resources used by a single call to \fBpcre_exec()\fR. The limit can be changed  
 at run time, as described in the \fBpcreapi\fR documentation. The default is 10  
 million, but this can be changed by adding a setting such as  
   
   --with-match-limit=500000  
   
 to the \fBconfigure\fR command.  
   
 .SH HANDLING VERY LARGE PATTERNS  
147  .rs  .rs
148  .sp  .sp
149  Within a compiled pattern, offset values are used to point from one part to  Within a compiled pattern, offset values are used to point from one part to
150  another (for example, from an opening parenthesis to an alternation  another (for example, from an opening parenthesis to an alternation
151  metacharacter). By default two-byte values are used for these offsets, leading  metacharacter). By default, two-byte values are used for these offsets, leading
152  to a maximum size for a compiled pattern of around 64K. This is sufficient to  to a maximum size for a compiled pattern of around 64K. This is sufficient to
153  handle all but the most gigantic patterns. Nevertheless, some people do want to  handle all but the most gigantic patterns. Nevertheless, some people do want to
154  process enormous patterns, so it is possible to compile PCRE to use three-byte  process enormous patterns, so it is possible to compile PCRE to use three-byte
155  or four-byte offsets by adding a setting such as  or four-byte offsets by adding a setting such as
156    .sp
157    --with-link-size=3    --with-link-size=3
158    .sp
159  to the \fBconfigure\fR command. The value given must be 2, 3, or 4. Using  to the \fBconfigure\fP command. The value given must be 2, 3, or 4. Using
160  longer offsets slows down the operation of PCRE because it has to load  longer offsets slows down the operation of PCRE because it has to load
161  additional bytes when handling them.  additional bytes when handling them.
162    .
163  If you build PCRE with an increased link size, test 2 (and test 5 if you are  .SH "AVOIDING EXCESSIVE STACK USAGE"
164  using UTF-8) will fail. Part of the output of these tests is a representation  .rs
165  of the compiled pattern, and this changes with the link size.  .sp
166    When matching with the \fBpcre_exec()\fP function, PCRE implements backtracking
167  .in 0  by making recursive calls to an internal function called \fBmatch()\fP. In
168  Last updated: 21 January 2003  environments where the size of the stack is limited, this can severely limit
169  .br  PCRE's operation. (The Unix environment does not usually suffer from this
170  Copyright (c) 1997-2003 University of Cambridge.  problem, but it may sometimes be necessary to increase the maximum stack size.
171    There is a discussion in the
172    .\" HREF
173    \fBpcrestack\fP
174    .\"
175    documentation.) An alternative approach to recursion that uses memory from the
176    heap to remember data, instead of using recursive function calls, has been
177    implemented to work round the problem of limited stack size. If you want to
178    build a version of PCRE that works this way, add
179    .sp
180      --disable-stack-for-recursion
181    .sp
182    to the \fBconfigure\fP command. With this configuration, PCRE will use the
183    \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory
184    management functions. By default these point to \fBmalloc()\fP and
185    \fBfree()\fP, but you can replace the pointers so that your own functions are
186    used.
187    .P
188    Separate functions are provided rather than using \fBpcre_malloc\fP and
189    \fBpcre_free\fP because the usage is very predictable: the block sizes
190    requested are always the same, and the blocks are always freed in reverse
191    order. A calling program might be able to implement optimized functions that
192    perform better than \fBmalloc()\fP and \fBfree()\fP. PCRE runs noticeably more
193    slowly when built in this way. This option affects only the \fBpcre_exec()\fP
194    function; it is not relevant for the the \fBpcre_dfa_exec()\fP function.
195    .
196    .SH "LIMITING PCRE RESOURCE USAGE"
197    .rs
198    .sp
199    Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly
200    (sometimes recursively) when matching a pattern with the \fBpcre_exec()\fP
201    function. By controlling the maximum number of times this function may be
202    called during a single matching operation, a limit can be placed on the
203    resources used by a single call to \fBpcre_exec()\fP. The limit can be changed
204    at run time, as described in the
205    .\" HREF
206    \fBpcreapi\fP
207    .\"
208    documentation. The default is 10 million, but this can be changed by adding a
209    setting such as
210    .sp
211      --with-match-limit=500000
212    .sp
213    to the \fBconfigure\fP command. This setting has no effect on the
214    \fBpcre_dfa_exec()\fP matching function.
215    .P
216    In some environments it is desirable to limit the depth of recursive calls of
217    \fBmatch()\fP more strictly than the total number of calls, in order to
218    restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
219    is specified) that is used. A second limit controls this; it defaults to the
220    value that is set for --with-match-limit, which imposes no additional
221    constraints. However, you can set a lower limit by adding, for example,
222    .sp
223      --with-match-limit-recursion=10000
224    .sp
225    to the \fBconfigure\fP command. This value can also be overridden at run time.
226    .
227    .SH "CREATING CHARACTER TABLES AT BUILD TIME"
228    .rs
229    .sp
230    PCRE uses fixed tables for processing characters whose code values are less
231    than 256. By default, PCRE is built with a set of tables that are distributed
232    in the file \fIpcre_chartables.c.dist\fP. These tables are for ASCII codes
233    only. If you add
234    .sp
235      --enable-rebuild-chartables
236    .sp
237    to the \fBconfigure\fP command, the distributed tables are no longer used.
238    Instead, a program called \fBdftables\fP is compiled and run. This outputs the
239    source for new set of tables, created in the default locale of your C runtime
240    system. (This method of replacing the tables does not work if you are cross
241    compiling, because \fBdftables\fP is run on the local host. If you need to
242    create alternative tables when cross compiling, you will have to do so "by
243    hand".)
244    .
245    .SH "USING EBCDIC CODE"
246    .rs
247    .sp
248    PCRE assumes by default that it will run in an environment where the character
249    code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
250    most computer operating systems. PCRE can, however, be compiled to run in an
251    EBCDIC environment by adding
252    .sp
253      --enable-ebcdic
254    .sp
255    to the \fBconfigure\fP command. This setting implies
256    --enable-rebuild-chartables. You should only use it if you know that you are in
257    an EBCDIC environment (for example, an IBM mainframe operating system).
258    .
259    .SH "PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT"
260    .rs
261    .sp
262    By default, \fBpcregrep\fP reads all files as plain text. You can build it so
263    that it recognizes files whose names end in \fB.gz\fP or \fB.bz2\fP, and reads
264    them with \fBlibz\fP or \fBlibbz2\fP, respectively, by adding one or both of
265    .sp
266      --enable-pcregrep-libz
267      --enable-pcregrep-libbz2
268    .sp
269    to the \fBconfigure\fP command. These options naturally require that the
270    relevant libraries are installed on your system. Configuration will fail if
271    they are not.
272    .
273    .SH "PCRETEST OPTION FOR LIBREADLINE SUPPORT"
274    .rs
275    .sp
276    If you add
277    .sp
278      --enable-pcretest-libreadline
279    .sp
280    to the \fBconfigure\fP command, \fBpcretest\fP is linked with the
281    \fBlibreadline\fP library, and when its input is from a terminal, it reads it
282    using the \fBreadline()\fP function. This provides line-editing and history
283    facilities. Note that \fBlibreadline\fP is GPL-licenced, so if you distribute a
284    binary of \fBpcretest\fP linked in this way, there may be licensing issues.
285    .P
286    Setting this option causes the \fB-lreadline\fP option to be added to the
287    \fBpcretest\fP build. In many operating environments with a sytem-installed
288    \fBlibreadline\fP this is sufficient. However, in some environments (e.g.
289    if an unmodified distribution version of readline is in use), some extra
290    configuration may be necessary. The INSTALL file for \fBlibreadline\fP says
291    this:
292    .sp
293      "Readline uses the termcap functions, but does not link with the
294      termcap or curses library itself, allowing applications which link
295      with readline the to choose an appropriate library."
296    .sp
297    If your environment has not been set up so that an appropriate library is
298    automatically included, you may need to add something like
299    .sp
300      LIBS="-ncurses"
301    .sp
302    immediately before the \fBconfigure\fP command.
303    .
304    .
305    .SH "SEE ALSO"
306    .rs
307    .sp
308    \fBpcreapi\fP(3), \fBpcre_config\fP(3).
309    .
310    .
311    .SH AUTHOR
312    .rs
313    .sp
314    .nf
315    Philip Hazel
316    University Computing Service
317    Cambridge CB2 3QH, England.
318    .fi
319    .
320    .
321    .SH REVISION
322    .rs
323    .sp
324    .nf
325    Last updated: 13 April 2008
326    Copyright (c) 1997-2008 University of Cambridge.
327    .fi

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