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1  README file for PCRE (Perl-compatible regular expressions)  README file for PCRE (Perl-compatible regular expression library)
2  ----------------------------------------------------------  -----------------------------------------------------------------
3    
4  *******************************************************************************  The latest release of PCRE is always available from
 *           IMPORTANT FOR THOSE UPGRADING FROM VERSIONS BEFORE 2.00           *  
 *                                                                             *  
 * Please note that there has been a change in the API such that a larger      *  
 * ovector is required at matching time, to provide some additional workspace. *  
 * The new man page has details. This change was necessary in order to support *  
 * some of the new functionality in Perl 5.005.                                *  
 *                                                                             *  
 *           IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.00                   *  
 *                                                                             *  
 * Another (I hope this is the last!) change has been made to the API for the  *  
 * pcre_compile() function. An additional argument has been added to make it   *  
 * possible to pass over a pointer to character tables built in the current    *  
 * locale by pcre_maketables(). To use the default tables, this new arguement  *  
 * should be passed as NULL.                                                   *  
 *                                                                             *  
 *           IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.05                   *  
 *                                                                             *  
 * Yet another (and again I hope this really is the last) change has been made *  
 * to the API for the pcre_exec() function. An additional argument has been    *  
 * added to make it possible to start the match other than at the start of the *  
 * subject string. This is important if there are lookbehinds. The new man     *  
 * page has the details, but you just want to convert existing programs, all   *  
 * you need to do is to stick in a new fifth argument to pcre_exec(), with a   *  
 * value of zero. For example, change                                          *  
 *                                                                             *  
 *   pcre_exec(pattern, extra, subject, length, options, ovec, ovecsize)       *  
 * to                                                                          *  
 *   pcre_exec(pattern, extra, subject, length, 0, options, ovec, ovecsize)    *  
 *******************************************************************************  
5    
6      ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.gz
7    
8  The distribution should contain the following files:  Please read the NEWS file if you are upgrading from a previous release.
9    
10    PCRE has its own native API, but a set of "wrapper" functions that are based on
11    the POSIX API are also supplied in the library libpcreposix. Note that this
12    just provides a POSIX calling interface to PCRE: the regular expressions
13    themselves still follow Perl syntax and semantics. The header file
14    for the POSIX-style functions is called pcreposix.h. The official POSIX name is
15    regex.h, but I didn't want to risk possible problems with existing files of
16    that name by distributing it that way. To use it with an existing program that
17    uses the POSIX API, it will have to be renamed or pointed at by a link.
18    
19    
20    Contributions by users of PCRE
21    ------------------------------
22    
23    You can find contributions from PCRE users in the directory
24    
25      ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib
26    
27    where there is also a README file giving brief descriptions of what they are.
28    Several of them provide support for compiling PCRE on various flavours of
29    Windows systems (I myself do not use Windows). Some are complete in themselves;
30    others are pointers to URLs containing relevant files.
31    
32    
33    Building PCRE on a Unix-like system
34    -----------------------------------
35    
36    To build PCRE on a Unix-like system, first run the "configure" command from the
37    PCRE distribution directory, with your current directory set to the directory
38    where you want the files to be created. This command is a standard GNU
39    "autoconf" configuration script, for which generic instructions are supplied in
40    INSTALL.
41    
42    Most commonly, people build PCRE within its own distribution directory, and in
43    this case, on many systems, just running "./configure" is sufficient, but the
44    usual methods of changing standard defaults are available. For example,
45    
46    CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local
47    
48    specifies that the C compiler should be run with the flags '-O2 -Wall' instead
49    of the default, and that "make install" should install PCRE under /opt/local
50    instead of the default /usr/local.
51    
52    If you want to build in a different directory, just run "configure" with that
53    directory as current. For example, suppose you have unpacked the PCRE source
54    into /source/pcre/pcre-xxx, but you want to build it in /build/pcre/pcre-xxx:
55    
56    cd /build/pcre/pcre-xxx
57    /source/pcre/pcre-xxx/configure
58    
59    There are some optional features that can be included or omitted from the PCRE
60    library. You can read more about them in the pcrebuild man page.
61    
62    . If you want to make use of the support for UTF-8 character strings in PCRE,
63      you must add --enable-utf8 to the "configure" command. Without it, the code
64      for handling UTF-8 is not included in the library. (Even when included, it
65      still has to be enabled by an option at run time.)
66    
67    . You can build PCRE to recognized CR or NL as the newline character, instead
68      of whatever your compiler uses for "\n", by adding --newline-is-cr or
69      --newline-is-nl to the "configure" command, respectively. Only do this if you
70      really understand what you are doing. On traditional Unix-like systems, the
71      newline character is NL.
72    
73    . When called via the POSIX interface, PCRE uses malloc() to get additional
74      storage for processing capturing parentheses if there are more than 10 of
75      them. You can increase this threshold by setting, for example,
76    
77      --with-posix-malloc-threshold=20
78    
79      on the "configure" command.
80    
81    . PCRE has a counter which can be set to limit the amount of resources it uses.
82      If the limit is exceeded during a match, the match fails. The default is ten
83      million. You can change the default by setting, for example,
84    
85      --with-match-limit=500000
86    
87      on the "configure" command. This is just the default; individual calls to
88      pcre_exec() can supply their own value. There is discussion on the pcreapi
89      man page.
90    
91    . The default maximum compiled pattern size is around 64K. You can increase
92      this by adding --with-link-size=3 to the "configure" command. You can
93      increase it even more by setting --with-link-size=4, but this is unlikely
94      ever to be necessary. If you build PCRE with an increased link size, test 2
95      (and 5 if you are using UTF-8) will fail. Part of the output of these tests
96      is a representation of the compiled pattern, and this changes with the link
97      size.
98    
99    The "configure" script builds five files:
100    
101    . libtool is a script that builds shared and/or static libraries
102    . Makefile is built by copying Makefile.in and making substitutions.
103    . config.h is built by copying config.in and making substitutions.
104    . pcre-config is built by copying pcre-config.in and making substitutions.
105    . RunTest is a script for running tests
106    
107    Once "configure" has run, you can run "make". It builds two libraries called
108    libpcre and libpcreposix, a test program called pcretest, and the pcregrep
109    command. You can use "make install" to copy these, the public header files
110    pcre.h and pcreposix.h, and the man pages to appropriate live directories on
111    your system, in the normal way.
112    
113    Running "make install" also installs the command pcre-config, which can be used
114    to recall information about the PCRE configuration and installation. For
115    example,
116    
117      pcre-config --version
118    
119    ChangeLog         log of changes to the code  prints the version number, and
   LICENCE           conditions for the use of PCRE  
   Makefile          for building PCRE  
   README            this file  
   RunTest           a shell script for running tests  
   Tech.Notes        notes on the encoding  
   pcre.3            man page for the functions  
   pcreposix.3       man page for the POSIX wrapper API  
   dftables.c        auxiliary program for building chartables.c  
   get.c             )  
   maketables.c      )  
   study.c           ) source of  
   pcre.c            )   the functions  
   pcreposix.c       )  
   pcre.h            header for the external API  
   pcreposix.h       header for the external POSIX wrapper API  
   internal.h        header for internal use  
   pcretest.c        test program  
   pgrep.1           man page for pgrep  
   pgrep.c           source of a grep utility that uses PCRE  
   perltest          Perl test program  
   testinput1        test data, compatible with Perl 5.004 and 5.005  
   testinput2        test data for error messages and non-Perl things  
   testinput3        test data, compatible with Perl 5.005  
   testinput4        test data for locale-specific tests  
   testoutput1       test results corresponding to testinput1  
   testoutput2       test results corresponding to testinput2  
   testoutput3       test results corresponding to testinput3  
   testoutput4       test results corresponding to testinput4  
   
 To build PCRE, edit Makefile for your system (it is a fairly simple make file,  
 and there are some comments at the top) and then run it. It builds two  
 libraries called libpcre.a and libpcreposix.a, a test program called pcretest,  
 and the pgrep command.  
   
 To test PCRE, run the RunTest script in the pcre directory. This runs pcretest  
 on each of the testinput files in turn, and compares the output with the  
 contents of the corresponding testoutput file. A file called testtry is used to  
 hold the output from pcretest (which is documented below).  
   
 To run pcretest on just one of the test files, give its number as an argument  
 to RunTest, for example:  
   
   RunTest 3  
   
 The first and third test files can also be fed directly into the perltest  
 program to check that Perl gives the same results. The third file requires the  
 additional features of release 5.005, which is why it is kept separate from the  
 main test input, which needs only Perl 5.004. In the long run, when 5.005 is  
 widespread, these two test files may get amalgamated.  
   
 The second set of tests check pcre_info(), pcre_study(), pcre_copy_substring(),  
 pcre_get_substring(), pcre_get_substring_list(), error detection and run-time  
 flags that are specific to PCRE, as well as the POSIX wrapper API.  
120    
121  The fourth set of tests checks pcre_maketables(), the facility for building a   pcre-config --libs
122    
123    outputs information about where the library is installed. This command can be
124    included in makefiles for programs that use PCRE, saving the programmer from
125    having to remember too many details.
126    
127    
128    Cross-compiling PCRE on a Unix-like system
129    ------------------------------------------
130    
131    PCRE needs to compile and run an auxiliary program as part of the building
132    process. Obviously, if the real compilation is for some other system, it can't
133    use the same CC and CFLAGS values when it is doing this. For cross compilation,
134    therefore, you must set CC_FOR_BUILD to the local host's compiler, and you can
135    set flags in CFLAGS_FOR_BUILD if you need to.
136    
137    
138    Shared libraries on Unix-like systems
139    -------------------------------------
140    
141    The default distribution builds PCRE as two shared libraries and two static
142    libraries, as long as the operating system supports shared libraries. Shared
143    library support relies on the "libtool" script which is built as part of the
144    "configure" process.
145    
146    The libtool script is used to compile and link both shared and static
147    libraries. They are placed in a subdirectory called .libs when they are newly
148    built. The programs pcretest and pcregrep are built to use these uninstalled
149    libraries (by means of wrapper scripts in the case of shared libraries). When
150    you use "make install" to install shared libraries, pcregrep and pcretest are
151    automatically re-built to use the newly installed shared libraries before being
152    installed themselves. However, the versions left in the source directory still
153    use the uninstalled libraries.
154    
155    To build PCRE using static libraries only you must use --disable-shared when
156    configuring it. For example
157    
158    ./configure --prefix=/usr/gnu --disable-shared
159    
160    Then run "make" in the usual way. Similarly, you can use --disable-static to
161    build only shared libraries.
162    
163    
164    Cross-compiling on a Unix-like system
165    -------------------------------------
166    
167    You can specify CC and CFLAGS in the normal way to the "configure" command, in
168    order to cross-compile PCRE for some other host. However, during the building
169    process, the dftables.c source file is compiled *and run* on the local host, in
170    order to generate the default character tables (the chartables.c file). It
171    therefore needs to be compiled with the local compiler, not the cross compiler.
172    You can do this by specifying HOST_CC (and if necessary HOST_CFLAGS) when
173    calling the "configure" command. If they are not specified, they default to the
174    values of CC and CFLAGS.
175    
176    
177    Building on non-Unix systems
178    ----------------------------
179    
180    For a non-Unix system, read the comments in the file NON-UNIX-USE. PCRE has
181    been compiled on Windows systems and on Macintoshes, but I don't know the
182    details because I don't use those systems. It should be straightforward to
183    build PCRE on any system that has a Standard C compiler, because it uses only
184    Standard C functions.
185    
186    
187    Testing PCRE
188    ------------
189    
190    To test PCRE on a Unix system, run the RunTest script that is created by the
191    configuring process. (This can also be run by "make runtest", "make check", or
192    "make test".) For other systems, see the instruction in NON-UNIX-USE.
193    
194    The script runs the pcretest test program (which is documented in its own man
195    page) on each of the testinput files (in the testdata directory) in turn,
196    and compares the output with the contents of the corresponding testoutput file.
197    A file called testtry is used to hold the output from pcretest. To run pcretest
198    on just one of the test files, give its number as an argument to RunTest, for
199    example:
200    
201      RunTest 2
202    
203    The first file can also be fed directly into the perltest script to check that
204    Perl gives the same results. The only difference you should see is in the first
205    few lines, where the Perl version is given instead of the PCRE version.
206    
207    The second set of tests check pcre_fullinfo(), pcre_info(), pcre_study(),
208    pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error
209    detection, and run-time flags that are specific to PCRE, as well as the POSIX
210    wrapper API. It also uses the debugging flag to check some of the internals of
211    pcre_compile().
212    
213    If you build PCRE with a locale setting that is not the standard C locale, the
214    character tables may be different (see next paragraph). In some cases, this may
215    cause failures in the second set of tests. For example, in a locale where the
216    isprint() function yields TRUE for characters in the range 128-255, the use of
217    [:isascii:] inside a character class defines a different set of characters, and
218    this shows up in this test as a difference in the compiled code, which is being
219    listed for checking. Where the comparison test output contains [\x00-\x7f] the
220    test will contain [\x00-\xff], and similarly in some other cases. This is not a
221    bug in PCRE.
222    
223    The third set of tests checks pcre_maketables(), the facility for building a
224  set of character tables for a specific locale and using them instead of the  set of character tables for a specific locale and using them instead of the
225  default tables. The tests make use of the "fr" (French) locale. Before running  default tables. The tests make use of the "fr" (French) locale. Before running
226  the test, the script checks for the presence of this locale by running the  the test, the script checks for the presence of this locale by running the
227  "locale" command. If that command fails, or if it doesn't include "fr" in the  "locale" command. If that command fails, or if it doesn't include "fr" in the
228  list of available locales, the fourth test cannot be run, and a comment is  list of available locales, the third test cannot be run, and a comment is
229  output to say why. If running this test produces instances of the error  output to say why. If running this test produces instances of the error
230    
231    ** Failed to set locale "fr"    ** Failed to set locale "fr"
# Line 103  output to say why. If running this test Line 233  output to say why. If running this test
233  in the comparison output, it means that locale is not available on your system,  in the comparison output, it means that locale is not available on your system,
234  despite being listed by "locale". This does not mean that PCRE is broken.  despite being listed by "locale". This does not mean that PCRE is broken.
235    
236  To install PCRE, copy libpcre.a to any suitable library directory (e.g.  The fourth test checks the UTF-8 support. It is not run automatically unless
237  /usr/local/lib), pcre.h to any suitable include directory (e.g.  PCRE is built with UTF-8 support. To do this you must set --enable-utf8 when
238  /usr/local/include), and pcre.3 to any suitable man directory (e.g.  running "configure". This file can be also fed directly to the perltest script,
239  /usr/local/man/man3).  provided you are running Perl 5.8 or higher. (For Perl 5.6, a small patch,
240    commented in the script, can be be used.)
 To install the pgrep command, copy it to any suitable binary directory, (e.g.  
 /usr/local/bin) and pgrep.1 to any suitable man directory (e.g.  
 /usr/local/man/man1).  
241    
242  PCRE has its own native API, but a set of "wrapper" functions that are based on  The fifth and final file tests error handling with UTF-8 encoding, and internal
243  the POSIX API are also supplied in the library libpcreposix.a. Note that this  UTF-8 features of PCRE that are not relevant to Perl.
 just provides a POSIX calling interface to PCRE: the regular expressions  
 themselves still follow Perl syntax and semantics. The header file  
 for the POSIX-style functions is called pcreposix.h. The official POSIX name is  
 regex.h, but I didn't want to risk possible problems with existing files of  
 that name by distributing it that way. To use it with an existing program that  
 uses the POSIX API, it will have to be renamed or pointed at by a link.  
244    
245    
246  Character tables  Character tables
# Line 161  You should not alter the set of characte Line 282  You should not alter the set of characte
282  will cause PCRE to malfunction.  will cause PCRE to malfunction.
283    
284    
285  The pcretest program  Manifest
286  --------------------  --------
   
 This program is intended for testing PCRE, but it can also be used for  
 experimenting with regular expressions.  
287    
288  If it is given two filename arguments, it reads from the first and writes to  The distribution should contain the following files:
 the second. If it is given only one filename argument, it reads from that file  
 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and  
 prompts for each line of input.  
   
 The program handles any number of sets of input on a single input file. Each  
 set starts with a regular expression, and continues with any number of data  
 lines to be matched against the pattern. An empty line signals the end of the  
 set. The regular expressions are given enclosed in any non-alphameric  
 delimiters other than backslash, for example  
   
   /(a|bc)x+yz/  
   
 White space before the initial delimiter is ignored. A regular expression may  
 be continued over several input lines, in which case the newline characters are  
 included within it. See the testinput files for many examples. It is possible  
 to include the delimiter within the pattern by escaping it, for example  
   
   /abc\/def/  
   
 If you do so, the escape and the delimiter form part of the pattern, but since  
 delimiters are always non-alphameric, this does not affect its interpretation.  
 If the terminating delimiter is immediately followed by a backslash, for  
 example,  
   
   /abc/\  
289    
290  then a backslash is added to the end of the pattern. This is done to provide a  (A) The actual source files of the PCRE library functions and their
291  way of testing the error condition that arises if a pattern finishes with a      headers:
 backslash, because  
292    
293    /abc\/    dftables.c            auxiliary program for building chartables.c
294      get.c                 )
295      maketables.c          )
296      study.c               ) source of
297      pcre.c                )   the functions
298      pcreposix.c           )
299      printint.c            )
300      pcre.in               "source" for the header for the external API; pcre.h
301                              is built from this by "configure"
302      pcreposix.h           header for the external POSIX wrapper API
303      internal.h            header for internal use
304      config.in             template for config.h, which is built by configure
305    
306    (B) Auxiliary files:
307    
308      AUTHORS               information about the author of PCRE
309      ChangeLog             log of changes to the code
310      INSTALL               generic installation instructions
311      LICENCE               conditions for the use of PCRE
312      COPYING               the same, using GNU's standard name
313      Makefile.in           template for Unix Makefile, which is built by configure
314      NEWS                  important changes in this release
315      NON-UNIX-USE          notes on building PCRE on non-Unix systems
316      README                this file
317      RunTest.in            template for a Unix shell script for running tests
318      config.guess          ) files used by libtool,
319      config.sub            )   used only when building a shared library
320      configure             a configuring shell script (built by autoconf)
321      configure.in          the autoconf input used to build configure
322      doc/Tech.Notes        notes on the encoding
323      doc/*.3               man page sources for the PCRE functions
324      doc/*.1               man page sources for pcregrep and pcretest
325      doc/html/*            HTML documentation
326      doc/pcre.txt          plain text version of the man pages
327      doc/pcretest.txt      plain text documentation of test program
328      doc/perltest.txt      plain text documentation of Perl test program
329      install-sh            a shell script for installing files
330      ltmain.sh             file used to build a libtool script
331      pcretest.c            comprehensive test program
332      pcredemo.c            simple demonstration of coding calls to PCRE
333      perltest              Perl test program
334      pcregrep.c            source of a grep utility that uses PCRE
335      pcre-config.in        source of script which retains PCRE information
336      testdata/testinput1   test data, compatible with Perl
337      testdata/testinput2   test data for error messages and non-Perl things
338      testdata/testinput3   test data for locale-specific tests
339      testdata/testinput4   test data for UTF-8 tests compatible with Perl
340      testdata/testinput5   test data for other UTF-8 tests
341      testdata/testoutput1  test results corresponding to testinput1
342      testdata/testoutput2  test results corresponding to testinput2
343      testdata/testoutput3  test results corresponding to testinput3
344      testdata/testoutput4  test results corresponding to testinput4
345      testdata/testoutput5  test results corresponding to testinput5
346    
347  is interpreted as the first line of a pattern that starts with "abc/", causing  (C) Auxiliary files for Win32 DLL
 pcretest to read the next line as a continuation of the regular expression.  
348    
349  The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,    dll.mk
350  PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For    pcre.def
 example:  
351    
352    /caseless/i  (D) Auxiliary file for VPASCAL
353    
354  These modifier letters have the same effect as they do in Perl. There are    makevp.bat
 others which set PCRE options that do not correspond to anything in Perl: /A,  
 /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.  
   
 Searching for all possible matches within each subject string can be requested  
 by the /g or /G modifier. The /g modifier behaves similarly to the way it does  
 in Perl. After finding a match, PCRE is called again to search the remainder of  
 the subject string. The difference between /g and /G is that the former uses  
 the start_offset argument to pcre_exec() to start searching at a new point  
 within the entire string, whereas the latter passes over a shortened substring.  
 This makes a difference to the matching process if the pattern begins with a  
 lookbehind assertion (including \b or \B).  
   
 There are a number of other modifiers for controlling the way pcretest  
 operates.  
   
 The /+ modifier requests that as well as outputting the substring that matched  
 the entire pattern, pcretest should in addition output the remainder of the  
 subject string. This is useful for tests where the subject contains multiple  
 copies of the same substring.  
   
 The /L modifier must be followed directly by the name of a locale, for example,  
   
   /pattern/Lfr  
   
 For this reason, it must be the last modifier letter. The given locale is set,  
 pcre_maketables() is called to build a set of character tables for the locale,  
 and this is then passed to pcre_compile() when compiling the regular  
 expression. Without an /L modifier, NULL is passed as the tables pointer; that  
 is, /L applies only to the expression on which it appears.  
   
 The /I modifier requests that pcretest output information about the compiled  
 expression (whether it is anchored, has a fixed first character, and so on). It  
 does this by calling pcre_info() after compiling an expression, and outputting  
 the information it gets back. If the pattern is studied, the results of that  
 are also output.  
   
 The /D modifier is a PCRE debugging feature, which also assumes /I. It causes  
 the internal form of compiled regular expressions to be output after  
 compilation.  
   
 The /S modifier causes pcre_study() to be called after the expression has been  
 compiled, and the results used when the expression is matched.  
   
 The /M modifier causes information about the size of memory block used to hold  
 the compile pattern to be output.  
   
 Finally, the /P modifier causes pcretest to call PCRE via the POSIX wrapper API  
 rather than its native API. When this is done, all other modifiers except /i,  
 /m, and /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is  
 set if /m is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always,  
 and PCRE_DOTALL unless REG_NEWLINE is set.  
   
 Before each data line is passed to pcre_exec(), leading and trailing whitespace  
 is removed, and it is then scanned for \ escapes. The following are recognized:  
   
   \a     alarm (= BEL)  
   \b     backspace  
   \e     escape  
   \f     formfeed  
   \n     newline  
   \r     carriage return  
   \t     tab  
   \v     vertical tab  
   \nnn   octal character (up to 3 octal digits)  
   \xhh   hexadecimal character (up to 2 hex digits)  
   
   \A     pass the PCRE_ANCHORED option to pcre_exec()  
   \B     pass the PCRE_NOTBOL option to pcre_exec()  
   \Cdd   call pcre_copy_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \Gdd   call pcre_get_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \L     call pcre_get_substringlist() after a successful match  
   \Odd   set the size of the output vector passed to pcre_exec() to dd  
            (any number of decimal digits)  
   \Z     pass the PCRE_NOTEOL option to pcre_exec()  
   
 A backslash followed by anything else just escapes the anything else. If the  
 very last character is a backslash, it is ignored. This gives a way of passing  
 an empty line as data, since a real empty line terminates the data input.  
   
 If /P was present on the regex, causing the POSIX wrapper API to be used, only  
 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to  
 regexec() respectively.  
   
 When a match succeeds, pcretest outputs the list of captured substrings that  
 pcre_exec() returns, starting with number 0 for the string that matched the  
 whole pattern. Here is an example of an interactive pcretest run.  
   
   $ pcretest  
   PCRE version 2.06 08-Jun-1999  
   
     re> /^abc(\d+)/  
   data> abc123  
    0: abc123  
    1: 123  
   data> xyz  
   No match  
   
 If the strings contain any non-printing characters, they are output as \0x  
 escapes. If the pattern has the /+ modifier, then the output for substring 0 is  
 followed by the the rest of the subject string, identified by "0+" like this:  
   
     re> /cat/+  
   data> cataract  
    0: cat  
    0+ aract  
   
 If the pattern has the /g or /G modifier, the results of successive matching  
 attempts are output in sequence, like this:  
   
     re> /\Bi(\w\w)/g  
   data> Mississippi  
    0: iss  
    1: ss  
    0: iss  
    1: ss  
    0: ipp  
    1: pp  
   
 "No match" is output only if the first match attempt fails.  
   
 If any of \C, \G, or \L are present in a data line that is successfully  
 matched, the substrings extracted by the convenience functions are output with  
 C, G, or L after the string number instead of a colon. This is in addition to  
 the normal full list. The string length (that is, the return from the  
 extraction function) is given in parentheses after each string for \C and \G.  
   
 Note that while patterns can be continued over several lines (a plain ">"  
 prompt is used for continuations), data lines may not. However newlines can be  
 included in data by means of the \n escape.  
   
 If the -p option is given to pcretest, it is equivalent to adding /P to each  
 regular expression: the POSIX wrapper API is used to call PCRE. None of the  
 following flags has any effect in this case.  
   
 If the option -d is given to pcretest, it is equivalent to adding /D to each  
 regular expression: the internal form is output after compilation.  
   
 If the option -i is given to pcretest, it is equivalent to adding /I to each  
 regular expression: information about the compiled pattern is given after  
 compilation.  
   
 If the option -m is given to pcretest, it outputs the size of each compiled  
 pattern after it has been compiled. It is equivalent to adding /M to each  
 regular expression. For compatibility with earlier versions of pcretest, -s is  
 a synonym for -m.  
   
 If the -t option is given, each compile, study, and match is run 20000 times  
 while being timed, and the resulting time per compile or match is output in  
 milliseconds. Do not set -t with -s, because you will then get the size output  
 20000 times and the timing will be distorted. If you want to change the number  
 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of  
 pcretest.c  
   
   
   
 The perltest program  
 --------------------  
   
 The perltest program tests Perl's regular expressions; it has the same  
 specification as pcretest, and so can be given identical input, except that  
 input patterns can be followed only by Perl's lower case modifiers. The  
 contents of testinput1 and testinput3 meet this condition.  
   
 The data lines are processed as Perl strings, so if they contain $ or @  
 characters, these have to be escaped. For this reason, all such characters in  
 testinput1 and testinput3 are escaped so that they can be used for perltest as  
 well as for pcretest, and the special upper case modifiers such as /A that  
 pcretest recognizes are not used in these files. The output should be  
 identical, apart from the initial identifying banner.  
   
 The testinput2 and testinput4 files are not suitable for feeding to perltest,  
 since they do make use of the special upper case modifiers and escapes that  
 pcretest uses to test some features of PCRE. The first of these files also  
 contains malformed regular expressions, in order to check that PCRE diagnoses  
 them correctly.  
355    
356  Philip Hazel <ph10@cam.ac.uk>  Philip Hazel <ph10@cam.ac.uk>
357  June 1999  February 2003
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