| .TH PCREBUILD 3 |
| .SH NAME |
| PCRE - Perl-compatible regular expressions |
| . |
| . |
| .SH "PCRE BUILD-TIME OPTIONS" |
| .rs |
| .sp |
| This document describes the optional features of PCRE that can be selected when |
| the library is compiled. It assumes use of the \fBconfigure\fP script, where |
| the optional features are selected or deselected by providing options to |
| \fBconfigure\fP before running the \fBmake\fP command. However, the same |
| options can be selected in both Unix-like and non-Unix-like environments using |
| the GUI facility of \fBcmake-gui\fP if you are using \fBCMake\fP instead of |
| \fBconfigure\fP to build PCRE. |
| .P |
| There is a lot more information about building PCRE in non-Unix-like |
| environments in the file called \fINON_UNIX_USE\fP, which is part of the PCRE |
| distribution. You should consult this file as well as the \fIREADME\fP file if |
| you are building in a non-Unix-like environment. |
| .P |
| The complete list of options for \fBconfigure\fP (which includes the standard |
| ones such as the selection of the installation directory) can be obtained by |
| running |
| .sp |
| ./configure --help |
| .sp |
| The following sections include descriptions of options whose names begin with |
| --enable or --disable. These settings specify changes to the defaults for the |
| \fBconfigure\fP command. Because of the way that \fBconfigure\fP works, |
| --enable and --disable always come in pairs, so the complementary option always |
| exists as well, but as it specifies the default, it is not described. |
| . |
| . |
| .SH "BUILDING SHARED AND STATIC LIBRARIES" |
| .rs |
| .sp |
| The PCRE building process uses \fBlibtool\fP to build both shared and static |
| Unix libraries by default. You can suppress one of these by adding one of |
| .sp |
| --disable-shared |
| --disable-static |
| .sp |
| to the \fBconfigure\fP command, as required. |
| . |
| . |
| .SH "C++ SUPPORT" |
| .rs |
| .sp |
| By default, the \fBconfigure\fP script will search for a C++ compiler and C++ |
| header files. If it finds them, it automatically builds the C++ wrapper library |
| for PCRE. You can disable this by adding |
| .sp |
| --disable-cpp |
| .sp |
| to the \fBconfigure\fP command. |
| . |
| . |
| .SH "UTF-8 SUPPORT" |
| .rs |
| .sp |
| To build PCRE with support for UTF-8 Unicode character strings, add |
| .sp |
| --enable-utf8 |
| .sp |
| to the \fBconfigure\fP command. Of itself, this does not make PCRE treat |
| strings as UTF-8. As well as compiling PCRE with this option, you also have |
| have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fP |
| or \fBpcre_compile2()\fP functions. |
| .P |
| If you set --enable-utf8 when compiling in an EBCDIC environment, PCRE expects |
| its input to be either ASCII or UTF-8 (depending on the runtime option). It is |
| not possible to support both EBCDIC and UTF-8 codes in the same version of the |
| library. Consequently, --enable-utf8 and --enable-ebcdic are mutually |
| exclusive. |
| . |
| . |
| .SH "UNICODE CHARACTER PROPERTY SUPPORT" |
| .rs |
| .sp |
| UTF-8 support allows PCRE to process character values greater than 255 in the |
| strings that it handles. On its own, however, it does not provide any |
| facilities for accessing the properties of such characters. If you want to be |
| able to use the pattern escapes \eP, \ep, and \eX, which refer to Unicode |
| character properties, you must add |
| .sp |
| --enable-unicode-properties |
| .sp |
| to the \fBconfigure\fP command. This implies UTF-8 support, even if you have |
| not explicitly requested it. |
| .P |
| Including Unicode property support adds around 30K of tables to the PCRE |
| library. Only the general category properties such as \fILu\fP and \fINd\fP are |
| supported. Details are given in the |
| .\" HREF |
| \fBpcrepattern\fP |
| .\" |
| documentation. |
| . |
| . |
| .SH "JUST-IN-TIME COMPILER SUPPORT" |
| .rs |
| .sp |
| Just-in-time compiler support is included in the build by specifying |
| .sp |
| --enable-jit |
| .sp |
| This support is available only for certain hardware architectures. If this |
| option is set for an unsupported architecture, a compile time error occurs. |
| See the |
| .\" HREF |
| \fBpcrejit\fP |
| .\" |
| documentation for a discussion of JIT usage. When JIT support is enabled, |
| pcregrep automatically makes use of it, unless you add |
| .sp |
| --disable-pcregrep-jit |
| .sp |
| to the "configure" command. |
| . |
| . |
| .SH "CODE VALUE OF NEWLINE" |
| .rs |
| .sp |
| By default, PCRE interprets the linefeed (LF) character as indicating the end |
| of a line. This is the normal newline character on Unix-like systems. You can |
| compile PCRE to use carriage return (CR) instead, by adding |
| .sp |
| --enable-newline-is-cr |
| .sp |
| to the \fBconfigure\fP command. There is also a --enable-newline-is-lf option, |
| which explicitly specifies linefeed as the newline character. |
| .sp |
| Alternatively, you can specify that line endings are to be indicated by the two |
| character sequence CRLF. If you want this, add |
| .sp |
| --enable-newline-is-crlf |
| .sp |
| to the \fBconfigure\fP command. There is a fourth option, specified by |
| .sp |
| --enable-newline-is-anycrlf |
| .sp |
| which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as |
| indicating a line ending. Finally, a fifth option, specified by |
| .sp |
| --enable-newline-is-any |
| .sp |
| causes PCRE to recognize any Unicode newline sequence. |
| .P |
| Whatever line ending convention is selected when PCRE is built can be |
| overridden when the library functions are called. At build time it is |
| conventional to use the standard for your operating system. |
| . |
| . |
| .SH "WHAT \eR MATCHES" |
| .rs |
| .sp |
| By default, the sequence \eR in a pattern matches any Unicode newline sequence, |
| whatever has been selected as the line ending sequence. If you specify |
| .sp |
| --enable-bsr-anycrlf |
| .sp |
| the default is changed so that \eR matches only CR, LF, or CRLF. Whatever is |
| selected when PCRE is built can be overridden when the library functions are |
| called. |
| . |
| . |
| .SH "POSIX MALLOC USAGE" |
| .rs |
| .sp |
| When PCRE is called through the POSIX interface (see the |
| .\" HREF |
| \fBpcreposix\fP |
| .\" |
| documentation), additional working storage is required for holding the pointers |
| to capturing substrings, because PCRE requires three integers per substring, |
| whereas the POSIX interface provides only two. If the number of expected |
| substrings is small, the wrapper function uses space on the stack, because this |
| is faster than using \fBmalloc()\fP for each call. The default threshold above |
| which the stack is no longer used is 10; it can be changed by adding a setting |
| such as |
| .sp |
| --with-posix-malloc-threshold=20 |
| .sp |
| to the \fBconfigure\fP command. |
| . |
| . |
| .SH "HANDLING VERY LARGE PATTERNS" |
| .rs |
| .sp |
| Within a compiled pattern, offset values are used to point from one part to |
| another (for example, from an opening parenthesis to an alternation |
| metacharacter). By default, two-byte values are used for these offsets, leading |
| to a maximum size for a compiled pattern of around 64K. This is sufficient to |
| handle all but the most gigantic patterns. Nevertheless, some people do want to |
| process truyl enormous patterns, so it is possible to compile PCRE to use |
| three-byte or four-byte offsets by adding a setting such as |
| .sp |
| --with-link-size=3 |
| .sp |
| to the \fBconfigure\fP command. The value given must be 2, 3, or 4. Using |
| longer offsets slows down the operation of PCRE because it has to load |
| additional bytes when handling them. |
| . |
| . |
| .SH "AVOIDING EXCESSIVE STACK USAGE" |
| .rs |
| .sp |
| When matching with the \fBpcre_exec()\fP function, PCRE implements backtracking |
| by making recursive calls to an internal function called \fBmatch()\fP. In |
| environments where the size of the stack is limited, this can severely limit |
| PCRE's operation. (The Unix environment does not usually suffer from this |
| problem, but it may sometimes be necessary to increase the maximum stack size. |
| There is a discussion in the |
| .\" HREF |
| \fBpcrestack\fP |
| .\" |
| documentation.) An alternative approach to recursion that uses memory from the |
| heap to remember data, instead of using recursive function calls, has been |
| implemented to work round the problem of limited stack size. If you want to |
| build a version of PCRE that works this way, add |
| .sp |
| --disable-stack-for-recursion |
| .sp |
| to the \fBconfigure\fP command. With this configuration, PCRE will use the |
| \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory |
| management functions. By default these point to \fBmalloc()\fP and |
| \fBfree()\fP, but you can replace the pointers so that your own functions are |
| used instead. |
| .P |
| Separate functions are provided rather than using \fBpcre_malloc\fP and |
| \fBpcre_free\fP because the usage is very predictable: the block sizes |
| requested are always the same, and the blocks are always freed in reverse |
| order. A calling program might be able to implement optimized functions that |
| perform better than \fBmalloc()\fP and \fBfree()\fP. PCRE runs noticeably more |
| slowly when built in this way. This option affects only the \fBpcre_exec()\fP |
| function; it is not relevant for \fBpcre_dfa_exec()\fP. |
| . |
| . |
| .SH "LIMITING PCRE RESOURCE USAGE" |
| .rs |
| .sp |
| Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly |
| (sometimes 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. |
| .P |
| In some environments it is desirable to limit the depth of recursive calls of |
| \fBmatch()\fP more strictly than the total number of calls, in order to |
| restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion |
| is specified) that is used. A second limit controls this; it defaults to the |
| value that is set for --with-match-limit, which imposes no additional |
| constraints. However, you can set a lower limit by adding, for example, |
| .sp |
| --with-match-limit-recursion=10000 |
| .sp |
| to the \fBconfigure\fP command. This value can also be overridden at run time. |
| . |
| . |
| .SH "CREATING CHARACTER TABLES AT BUILD TIME" |
| .rs |
| .sp |
| PCRE uses fixed tables for processing characters whose code values are less |
| than 256. By default, PCRE is built with a set of tables that are distributed |
| in the file \fIpcre_chartables.c.dist\fP. These tables are for ASCII codes |
| only. If you add |
| .sp |
| --enable-rebuild-chartables |
| .sp |
| to the \fBconfigure\fP command, the distributed tables are no longer used. |
| Instead, a program called \fBdftables\fP is compiled and run. This outputs the |
| source for new set of tables, created in the default locale of your C runtime |
| system. (This method of replacing the tables does not work if you are cross |
| compiling, because \fBdftables\fP is run on the local host. If you need to |
| create alternative tables when cross compiling, you will have to do so "by |
| hand".) |
| . |
| . |
| .SH "USING EBCDIC CODE" |
| .rs |
| .sp |
| PCRE assumes by default that it will run in an environment where the character |
| code is ASCII (or Unicode, which is a superset of ASCII). This is the case for |
| most computer operating systems. PCRE can, however, be compiled to run in an |
| EBCDIC environment by adding |
| .sp |
| --enable-ebcdic |
| .sp |
| to the \fBconfigure\fP command. This setting implies |
| --enable-rebuild-chartables. You should only use it if you know that you are in |
| an EBCDIC environment (for example, an IBM mainframe operating system). The |
| --enable-ebcdic option is incompatible with --enable-utf8. |
| . |
| . |
| .SH "PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT" |
| .rs |
| .sp |
| By default, \fBpcregrep\fP reads all files as plain text. You can build it so |
| that it recognizes files whose names end in \fB.gz\fP or \fB.bz2\fP, and reads |
| them with \fBlibz\fP or \fBlibbz2\fP, respectively, by adding one or both of |
| .sp |
| --enable-pcregrep-libz |
| --enable-pcregrep-libbz2 |
| .sp |
| to the \fBconfigure\fP command. These options naturally require that the |
| relevant libraries are installed on your system. Configuration will fail if |
| they are not. |
| . |
| . |
| .SH "PCREGREP BUFFER SIZE" |
| .rs |
| .sp |
| \fBpcregrep\fP uses an internal buffer to hold a "window" on the file it is |
| scanning, in order to be able to output "before" and "after" lines when it |
| finds a match. The size of the buffer is controlled by a parameter whose |
| default value is 20K. The buffer itself is three times this size, but because |
| of the way it is used for holding "before" lines, the longest line that is |
| guaranteed to be processable is the parameter size. You can change the default |
| parameter value by adding, for example, |
| .sp |
| --with-pcregrep-bufsize=50K |
| .sp |
| to the \fBconfigure\fP command. The caller of \fPpcregrep\fP can, however, |
| override this value by specifying a run-time option. |
| . |
| . |
| .SH "PCRETEST OPTION FOR LIBREADLINE SUPPORT" |
| .rs |
| .sp |
| If you add |
| .sp |
| --enable-pcretest-libreadline |
| .sp |
| to the \fBconfigure\fP command, \fBpcretest\fP is linked with the |
| \fBlibreadline\fP library, and when its input is from a terminal, it reads it |
| using the \fBreadline()\fP function. This provides line-editing and history |
| facilities. Note that \fBlibreadline\fP is GPL-licensed, so if you distribute a |
| binary of \fBpcretest\fP linked in this way, there may be licensing issues. |
| .P |
| Setting this option causes the \fB-lreadline\fP option to be added to the |
| \fBpcretest\fP build. In many operating environments with a sytem-installed |
| \fBlibreadline\fP this is sufficient. However, in some environments (e.g. |
| if an unmodified distribution version of readline is in use), some extra |
| configuration may be necessary. The INSTALL file for \fBlibreadline\fP says |
| this: |
| .sp |
| "Readline uses the termcap functions, but does not link with the |
| termcap or curses library itself, allowing applications which link |
| with readline the to choose an appropriate library." |
| .sp |
| If your environment has not been set up so that an appropriate library is |
| automatically included, you may need to add something like |
| .sp |
| LIBS="-ncurses" |
| .sp |
| immediately before the \fBconfigure\fP command. |
| . |
| . |
| .SH "SEE ALSO" |
| .rs |
| .sp |
| \fBpcreapi\fP(3), \fBpcre_config\fP(3). |
| . |
| . |
| .SH AUTHOR |
| .rs |
| .sp |
| .nf |
| Philip Hazel |
| University Computing Service |
| Cambridge CB2 3QH, England. |
| .fi |
| . |
| . |
| .SH REVISION |
| .rs |
| .sp |
| .nf |
| Last updated: 06 September 2011 |
| Copyright (c) 1997-2011 University of Cambridge. |
| .fi |