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revision 77 by nigel, Sat Feb 24 21:40:45 2007 UTC revision 260 by ph10, Thu Sep 20 10:19:16 2007 UTC
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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\fP script that is run before the \fBmake\fP  the optional features are selected or deselected by providing options to
10  command. The complete list of options for \fBconfigure\fP (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  .sp
19    ./configure --help    ./configure --help
20  .sp  .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\fP command. Because of the way that \fBconfigure\fP 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 "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"  .SH "UTF-8 SUPPORT"
39  .rs  .rs
40  .sp  .sp
# Line 45  character properties, you must add Line 61  character properties, you must add
61  to the \fBconfigure\fP command. This implies UTF-8 support, even if you have  to the \fBconfigure\fP command. This implies UTF-8 support, even if you have
62  not explicitly requested it.  not explicitly requested it.
63  .P  .P
64  Including Unicode property support adds around 90K of tables to the PCRE  Including Unicode property support adds around 30K of tables to the PCRE
65  library, approximately doubling its size. Only the general category properties  library. Only the general category properties such as \fILu\fP and \fINd\fP are
66  such as \fILu\fP and \fINd\fP are supported. Details are given in the  supported. Details are given in the
67  .\" HREF  .\" HREF
68  \fBpcrepattern\fP  \fBpcrepattern\fP
69  .\"  .\"
# Line 56  documentation. Line 72  documentation.
72  .SH "CODE VALUE OF NEWLINE"  .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  .sp
79    --enable-newline-is-cr    --enable-newline-is-cr
80  .sp  .sp
81  to the \fBconfigure\fP 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    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
106    .sp
107    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"  .SH "BUILDING SHARED AND STATIC LIBRARIES"
117  .rs  .rs
# Line 96  such as Line 143  such as
143  .sp  .sp
144  to the \fBconfigure\fP command.  to the \fBconfigure\fP command.
145  .  .
 .SH "LIMITING PCRE RESOURCE USAGE"  
 .rs  
 .sp  
 Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly  
 (possibly recursively) when matching a pattern with the \fBpcre_exec()\fP  
 function. By controlling the maximum number of times this function may be  
 called during a single matching operation, a limit can be placed on the  
 resources used by a single call to \fBpcre_exec()\fP. The limit can be changed  
 at run time, as described in the  
 .\" HREF  
 \fBpcreapi\fP  
 .\"  
 documentation. The default is 10 million, but this can be changed by adding a  
 setting such as  
 .sp  
   --with-match-limit=500000  
 .sp  
 to the \fBconfigure\fP command. This setting has no effect on the  
 \fBpcre_dfa_exec()\fP matching function.  
 .  
146  .SH "HANDLING VERY LARGE PATTERNS"  .SH "HANDLING VERY LARGE PATTERNS"
147  .rs  .rs
148  .sp  .sp
# Line 132  or four-byte offsets by adding a setting Line 159  or four-byte offsets by adding a setting
159  to the \fBconfigure\fP 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.
 .P  
 If you build PCRE with an increased link size, test 2 (and test 5 if you are  
 using UTF-8) will fail. Part of the output of these tests is a representation  
 of the compiled pattern, and this changes with the link size.  
162  .  .
163  .SH "AVOIDING EXCESSIVE STACK USAGE"  .SH "AVOIDING EXCESSIVE STACK USAGE"
164  .rs  .rs
# Line 144  When matching with the \fBpcre_exec()\fP Line 167  When matching with the \fBpcre_exec()\fP
167  by making recursive calls to an internal function called \fBmatch()\fP. In  by making recursive calls to an internal function called \fBmatch()\fP. In
168  environments where the size of the stack is limited, this can severely limit  environments where the size of the stack is limited, this can severely limit
169  PCRE's operation. (The Unix environment does not usually suffer from this  PCRE's operation. (The Unix environment does not usually suffer from this
170  problem.) An alternative approach that uses memory from the heap to remember  problem, but it may sometimes be necessary to increase the maximum stack size.
171  data, instead of using recursive function calls, has been implemented to work  There is a discussion in the
172  round this problem. If you want to build a version of PCRE that works this way,  .\" HREF
173  add  \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  .sp
180    --disable-stack-for-recursion    --disable-stack-for-recursion
181  .sp  .sp
182  to the \fBconfigure\fP command. With this configuration, PCRE will use the  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  \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory
184  management functions. Separate functions are provided because the usage is very  management functions. By default these point to \fBmalloc()\fP and
185  predictable: the block sizes requested are always the same, and the blocks are  \fBfree()\fP, but you can replace the pointers so that your own functions are
186  always freed in reverse order. A calling program might be able to implement  used.
187  optimized functions that perform better than the standard \fBmalloc()\fP and  .P
188  \fBfree()\fP functions. PCRE runs noticeably more slowly when built in this  Separate functions are provided rather than using \fBpcre_malloc\fP and
189  way. This option affects only the \fBpcre_exec()\fP function; it is not  \fBpcre_free\fP because the usage is very predictable: the block sizes
190  relevant for the the \fBpcre_dfa_exec()\fP function.  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"  .SH "USING EBCDIC CODE"
246  .rs  .rs
247  .sp  .sp
248  PCRE assumes by default that it will run in an environment where the character  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). PCRE can, however, be  code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
250  compiled to run in an EBCDIC environment by adding  most computer operating systems. PCRE can, however, be compiled to run in an
251    EBCDIC environment by adding
252  .sp  .sp
253    --enable-ebcdic    --enable-ebcdic
254  .sp  .sp
255  to the \fBconfigure\fP command.  to the \fBconfigure\fP command. This setting implies
256  .P  --enable-rebuild-chartables. You should only use it if you know that you are in
257  .in 0  an EBCDIC environment (for example, an IBM mainframe operating system).
258  Last updated: 28 February 2005  .
259  .br  .
260  Copyright (c) 1997-2005 University of Cambridge.  .SH "SEE ALSO"
261    .rs
262    .sp
263    \fBpcreapi\fP(3), \fBpcre_config\fP(3).
264    .
265    .
266    .SH AUTHOR
267    .rs
268    .sp
269    .nf
270    Philip Hazel
271    University Computing Service
272    Cambridge CB2 3QH, England.
273    .fi
274    .
275    .
276    .SH REVISION
277    .rs
278    .sp
279    .nf
280    Last updated: 21 September 2007
281    Copyright (c) 1997-2007 University of Cambridge.
282    .fi

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