1PCREBUILD(3) Library Functions Manual PCREBUILD(3)
2
6 PCRE - Perl-compatible regular expressions
7
9 This document describes the optional features of PCRE that can be
11 selected when the library is compiled. It assumes use of the configure
12 script, where the optional features are selected or deselected by pro‐
13 viding options to configure before running the make command. However,
14 the same options can be selected in both Unix-like and non-Unix-like
15 environments using the GUI facility of cmake-gui if you are using CMake
16 instead of configure to build PCRE.
17 There is a lot more information about building PCRE in non-Unix-like
19 environments in the file called NON_UNIX_USE, which is part of the PCRE
20 distribution. You should consult this file as well as the README file
21 if you are building in a non-Unix-like environment.
22 The complete list of options for configure (which includes the standard
24 ones such as the selection of the installation directory) can be
25 obtained by running
26 ./configure --help
28 The following sections include descriptions of options whose names
30 begin with --enable or --disable. These settings specify changes to the
31 defaults for the configure command. Because of the way that configure
32 works, --enable and --disable always come in pairs, so the complemen‐
33 tary option always exists as well, but as it specifies the default, it
34 is not described.
35
37 By default, the configure script will search for a C++ compiler and C++
39 header files. If it finds them, it automatically builds the C++ wrapper
40 library for PCRE. You can disable this by adding
41 --disable-cpp
43 to the configure command.
45
47 To build PCRE with support for UTF-8 Unicode character strings, add
49 --enable-utf8
51 to the configure command. Of itself, this does not make PCRE treat
53 strings as UTF-8. As well as compiling PCRE with this option, you also
54 have have to set the PCRE_UTF8 option when you call the pcre_compile()
55 or pcre_compile2() functions.
56 If you set --enable-utf8 when compiling in an EBCDIC environment, PCRE
58 expects its input to be either ASCII or UTF-8 (depending on the runtime
59 option). It is not possible to support both EBCDIC and UTF-8 codes in
60 the same version of the library. Consequently, --enable-utf8 and
61 --enable-ebcdic are mutually exclusive.
62
64 UTF-8 support allows PCRE to process character values greater than 255
66 in the strings that it handles. On its own, however, it does not pro‐
67 vide any facilities for accessing the properties of such characters. If
68 you want to be able to use the pattern escapes \P, \p, and \X, which
69 refer to Unicode character properties, you must add
70 --enable-unicode-properties
72 to the configure command. This implies UTF-8 support, even if you have
74 not explicitly requested it.
75 Including Unicode property support adds around 30K of tables to the
77 PCRE library. Only the general category properties such as Lu and Nd
78 are supported. Details are given in the pcrepattern documentation.
79
81 By default, PCRE interprets the linefeed (LF) character as indicating
83 the end of a line. This is the normal newline character on Unix-like
84 systems. You can compile PCRE to use carriage return (CR) instead, by
85 adding
86 --enable-newline-is-cr
88 to the configure command. There is also a --enable-newline-is-lf
90 option, which explicitly specifies linefeed as the newline character.
91 Alternatively, you can specify that line endings are to be indicated by
93 the two character sequence CRLF. If you want this, add
94 --enable-newline-is-crlf
96 to the configure command. There is a fourth option, specified by
98 --enable-newline-is-anycrlf
100 which causes PCRE to recognize any of the three sequences CR, LF, or
102 CRLF as indicating a line ending. Finally, a fifth option, specified by
103 --enable-newline-is-any
105 causes PCRE to recognize any Unicode newline sequence.
107 Whatever line ending convention is selected when PCRE is built can be
109 overridden when the library functions are called. At build time it is
110 conventional to use the standard for your operating system.
111
113 By default, the sequence \R in a pattern matches any Unicode newline
115 sequence, whatever has been selected as the line ending sequence. If
116 you specify
117 --enable-bsr-anycrlf
119 the default is changed so that \R matches only CR, LF, or CRLF. What‐
121 ever is selected when PCRE is built can be overridden when the library
122 functions are called.
123
125 The PCRE building process uses libtool to build both shared and static
127 Unix libraries by default. You can suppress one of these by adding one
128 of
129 --disable-shared
131 --disable-static
132 to the configure command, as required.
134
136 When PCRE is called through the POSIX interface (see the pcreposix doc‐
138 umentation), additional working storage is required for holding the
139 pointers to capturing substrings, because PCRE requires three integers
140 per substring, whereas the POSIX interface provides only two. If the
141 number of expected substrings is small, the wrapper function uses space
142 on the stack, because this is faster than using malloc() for each call.
143 The default threshold above which the stack is no longer used is 10; it
144 can be changed by adding a setting such as
145 --with-posix-malloc-threshold=20
147 to the configure command.
149
151 Within a compiled pattern, offset values are used to point from one
153 part to another (for example, from an opening parenthesis to an alter‐
154 nation metacharacter). By default, two-byte values are used for these
155 offsets, leading to a maximum size for a compiled pattern of around
156 64K. This is sufficient to handle all but the most gigantic patterns.
157 Nevertheless, some people do want to process truyl enormous patterns,
158 so it is possible to compile PCRE to use three-byte or four-byte off‐
159 sets by adding a setting such as
160 --with-link-size=3
162 to the configure command. The value given must be 2, 3, or 4. Using
164 longer offsets slows down the operation of PCRE because it has to load
165 additional bytes when handling them.
166
168 When matching with the pcre_exec() function, PCRE implements backtrack‐
170 ing by making recursive calls to an internal function called match().
171 In environments where the size of the stack is limited, this can se‐
172 verely limit PCRE's operation. (The Unix environment does not usually
173 suffer from this problem, but it may sometimes be necessary to increase
174 the maximum stack size. There is a discussion in the pcrestack docu‐
175 mentation.) An alternative approach to recursion that uses memory from
176 the heap to remember data, instead of using recursive function calls,
177 has been implemented to work round the problem of limited stack size.
178 If you want to build a version of PCRE that works this way, add
179 --disable-stack-for-recursion
181 to the configure command. With this configuration, PCRE will use the
183 pcre_stack_malloc and pcre_stack_free variables to call memory manage‐
184 ment functions. By default these point to malloc() and free(), but you
185 can replace the pointers so that your own functions are used instead.
186 Separate functions are provided rather than using pcre_malloc and
188 pcre_free because the usage is very predictable: the block sizes
189 requested are always the same, and the blocks are always freed in
190 reverse order. A calling program might be able to implement optimized
191 functions that perform better than malloc() and free(). PCRE runs
192 noticeably more slowly when built in this way. This option affects only
193 the pcre_exec() function; it is not relevant for pcre_dfa_exec().
194
196 Internally, PCRE has a function called match(), which it calls repeat‐
198 edly (sometimes recursively) when matching a pattern with the
199 pcre_exec() function. By controlling the maximum number of times this
200 function may be called during a single matching operation, a limit can
201 be placed on the resources used by a single call to pcre_exec(). The
202 limit can be changed at run time, as described in the pcreapi documen‐
203 tation. The default is 10 million, but this can be changed by adding a
204 setting such as
205 --with-match-limit=500000
207 to the configure command. This setting has no effect on the
209 pcre_dfa_exec() matching function.
210 In some environments it is desirable to limit the depth of recursive
212 calls of match() more strictly than the total number of calls, in order
213 to restrict the maximum amount of stack (or heap, if --disable-stack-
214 for-recursion is specified) that is used. A second limit controls this;
215 it defaults to the value that is set for --with-match-limit, which
216 imposes no additional constraints. However, you can set a lower limit
217 by adding, for example,
218 --with-match-limit-recursion=10000
220 to the configure command. This value can also be overridden at run
222 time.
223
225 PCRE uses fixed tables for processing characters whose code values are
227 less than 256. By default, PCRE is built with a set of tables that are
228 distributed in the file pcre_chartables.c.dist. These tables are for
229 ASCII codes only. If you add
230 --enable-rebuild-chartables
232 to the configure command, the distributed tables are no longer used.
234 Instead, a program called dftables is compiled and run. This outputs
235 the source for new set of tables, created in the default locale of your
236 C runtime system. (This method of replacing the tables does not work if
237 you are cross compiling, because dftables is run on the local host. If
238 you need to create alternative tables when cross compiling, you will
239 have to do so "by hand".)
240
242 PCRE assumes by default that it will run in an environment where the
244 character code is ASCII (or Unicode, which is a superset of ASCII).
245 This is the case for most computer operating systems. PCRE can, how‐
246 ever, be compiled to run in an EBCDIC environment by adding
247 --enable-ebcdic
249 to the configure command. This setting implies --enable-rebuild-charta‐
251 bles. You should only use it if you know that you are in an EBCDIC
252 environment (for example, an IBM mainframe operating system). The
253 --enable-ebcdic option is incompatible with --enable-utf8.
254
256 By default, pcregrep reads all files as plain text. You can build it so
258 that it recognizes files whose names end in .gz or .bz2, and reads them
259 with libz or libbz2, respectively, by adding one or both of
260 --enable-pcregrep-libz
262 --enable-pcregrep-libbz2
263 to the configure command. These options naturally require that the rel‐
265 evant libraries are installed on your system. Configuration will fail
266 if they are not.
267
269 If you add
271 --enable-pcretest-libreadline
273 to the configure command, pcretest is linked with the libreadline
275 library, and when its input is from a terminal, it reads it using the
276 readline() function. This provides line-editing and history facilities.
277 Note that libreadline is GPL-licensed, so if you distribute a binary of
278 pcretest linked in this way, there may be licensing issues.
279 Setting this option causes the -lreadline option to be added to the
281 pcretest build. In many operating environments with a sytem-installed
282 libreadline this is sufficient. However, in some environments (e.g. if
283 an unmodified distribution version of readline is in use), some extra
284 configuration may be necessary. The INSTALL file for libreadline says
285 this:
286 "Readline uses the termcap functions, but does not link with the
288 termcap or curses library itself, allowing applications which link
289 with readline the to choose an appropriate library."
290 If your environment has not been set up so that an appropriate library
292 is automatically included, you may need to add something like
293 LIBS="-ncurses"
295 immediately before the configure command.
297
299 pcreapi(3), pcre_config(3).
301
303 Philip Hazel
305 University Computing Service
306 Cambridge CB2 3QH, England.
307
309 Last updated: 29 September 2009
311 Copyright (c) 1997-2009 University of Cambridge.
312 PCREBUILD(3)