/[pcre]/code/tags/pcre-3.1/README

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-revision 3 by nigel,
Sat Feb 24 21:38:01 2007 UTC
+revision 35 by nigel,
Sat Feb 24 21:39:05 2007 UTC
 Line 1
  README file for PCRE (Perl-compatible regular expressions)
  ----------------------------------------------------------
+ *******************************************************************************
+ *           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)    *
+ *******************************************************************************
  The distribution should contain the following files:
    ChangeLog         log of changes to the code
+   LICENCE           conditions for the use of PCRE
    Makefile          for building PCRE
-   Performance       notes on performance
    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
-   maketables.c      auxiliary program for building chartables.c
+   dftables.c        auxiliary program for building chartables.c
+   get.c             )
+   maketables.c      )
    study.c           ) source of
    pcre.c            )   the functions
    pcreposix.c       )
-Line 21 
 The distribution should contain the foll
+Line 56 
 The distribution should contain the foll
    pgrep.1           man page for pgrep
    pgrep.c           source of a grep utility that uses PCRE
    perltest          Perl test program
-   testinput         test data, compatible with Perl
+   testinput1        test data, compatible with Perl 5.004 and 5.005
    testinput2        test data for error messages and non-Perl things
-   testoutput        test results corresponding to testinput
+   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.
+ The fourth set of tests checks pcre_maketables(), the facility for building a
+ set of character tables for a specific locale and using them instead of the
+ default tables. The tests make use of the "fr" (French) locale. Before running
+ the test, the script checks for the presence of this locale by running the
+ "locale" command. If that command fails, or if it doesn't include "fr" in the
+ list of available locales, the fourth test cannot be run, and a comment is
+ output to say why. If running this test produces instances of the error
+   ** Failed to set locale "fr"
- To build PCRE, edit Makefile for your system (it is a fairly simple make file)
+ in the comparison output, it means that locale is not available on your system,
- and then run it. It builds a two libraries called libpcre.a and libpcreposix.a,
+ despite being listed by "locale". This does not mean that PCRE is broken.
- a test program called pcretest, and the pgrep command.
- To test PCRE, run pcretest on the file testinput, and compare the output with
- the contents of testoutput. There should be no differences. For example:
-   pcretest testinput /tmp/anything
-   diff /tmp/anything testoutput
- Do the same with testinput2, comparing the output with testoutput2, but this
- time using the -i flag for pcretest, i.e.
-   pcretest -i testinput2 /tmp/anything
-   diff /tmp/anything testoutput2
- There are two sets of tests because the first set can also be fed directly into
- the perltest program to check that Perl gives the same results. The second set
- of tests check pcre_info(), pcre_study(), error detection and run-time flags
- that are specific to PCRE, as well as the POSIX wrapper API.
  To install PCRE, copy libpcre.a to any suitable library directory (e.g.
  /usr/local/lib), pcre.h to any suitable include directory (e.g.
-Line 63 
 themselves still follow Perl syntax and
+Line 119 
 themselves still follow Perl syntax and
  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.
+ uses the POSIX API, it will have to be renamed or pointed at by a link.
  Character tables
  ----------------
- PCRE uses four tables for manipulating and identifying characters. These are
+ PCRE uses four tables for manipulating and identifying characters. The final
- compiled from a source file called chartables.c. This is not supplied in
+ argument of the pcre_compile() function is a pointer to a block of memory
- the distribution, but is built by the program maketables (compiled from
+ containing the concatenated tables. A call to pcre_maketables() can be used to
- maketables.c), which uses the ANSI C character handling functions such as
+ generate a set of tables in the current locale. If the final argument for
- isalnum(), isalpha(), isupper(), islower(), etc. to build the table sources.
+ pcre_compile() is passed as NULL, a set of default tables that is built into
- This means that the default C locale set in your system may affect the contents
+ the binary is used.
- of the tables. You can change the tables by editing chartables.c and then
- re-building PCRE. If you do this, you should probably also edit Makefile to
+ The source file called chartables.c contains the default set of tables. This is
- ensure that the file doesn't ever get re-generated.
+ not supplied in the distribution, but is built by the program dftables
+ (compiled from dftables.c), which uses the ANSI C character handling functions
- The first two tables pcre_lcc[] and pcre_fcc[] provide lower casing and a
+ such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
- case flipping functions, respectively. The pcre_cbits[] table consists of four
+ sources. This means that the default C locale which is set for your system will
--byte bit maps which identify digits, letters, "word" characters, and white
+ control the contents of these default tables. You can change the default tables
- space, respectively. These are used when building 32-byte bit maps that
+ by editing chartables.c and then re-building PCRE. If you do this, you should
- represent character classes.
+ probably also edit Makefile to ensure that the file doesn't ever get
+ re-generated.
+ The first two 256-byte tables provide lower casing and case flipping functions,
+ respectively. The next table consists of three 32-byte bit maps which identify
+ digits, "word" characters, and white space, respectively. These are used when
+ building 32-byte bit maps that represent character classes.
- The pcre_ctypes[] table has bits indicating various character types, as
+ The final 256-byte table has bits indicating various character types, as
  follows:
   white space character
-Line 114 
 The program handles any number of sets o
+Line 176 
 The program handles any number of sets o
  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, for example
+ delimiters other than backslash, for example
    /(a|bc)x+yz/
- and may be followed by i, m, s, or x to set the PCRE_CASELESS, PCRE_MULTILINE,
+ White space before the initial delimiter is ignored. A regular expression may
- PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the
+ be continued over several input lines, in which case the newline characters are
- same effect as they do in Perl.
+ 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
- There are also some upper case options that do not match Perl options: /A, /E,
- and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
+   /abc\/def/
- The /D option is a PCRE debugging feature. It causes the internal form of
- compiled regular expressions to be output after compilation. The /S option
+ If you do so, the escape and the delimiter form part of the pattern, but since
- causes pcre_study() to be called after the expression has been compiled, and
+ delimiters are always non-alphameric, this does not affect its interpretation.
- the results used when the expression is matched. If /I is present as well as
+ If the terminating delimiter is immediately followed by a backslash, for
- /S, then pcre_study() is called with the PCRE_CASELESS option.
+ example,
- Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API
+   /abc/\
- rather than its native API. When this is done, all other options except /i and
- /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
+ then a backslash is added to the end of the pattern. This is done to provide a
- is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
+ way of testing the error condition that arises if a pattern finishes with a
- PCRE_DOTALL unless REG_NEWLINE is set.
+ backslash, because
- A regular expression can extend over several lines of input; the newlines are
+   /abc\/
- included in it. See the testinput file for many examples.
+ is interpreted as the first line of a pattern that starts with "abc/", causing
+ pcretest to read the next line as a continuation of the regular expression.
+ The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,
+ PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
+ example:
+   /caseless/i
+ These modifier letters have the same effect as they do in Perl. There are
+ 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:
-Line 155 
 is removed, and it is then scanned for \
+Line 278 
 is removed, and it is then scanned for \
    \A     pass the PCRE_ANCHORED option to pcre_exec()
    \B     pass the PCRE_NOTBOL option to pcre_exec()
-   \E     pass the PCRE_DOLLAR_ENDONLY option to pcre_exec()
+   \Cdd   call pcre_copy_substring() for substring dd after a successful match
-   \I     pass the PCRE_CASELESS option to pcre_exec()
+            (any decimal number less than 32)
-   \M     pass the PCRE_MULTILINE option to pcre_exec()
+   \Gdd   call pcre_get_substring() for substring dd after a successful match
-   \S     pass the PCRE_DOTALL option to pcre_exec()
+            (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()
-Line 171 
 If /P was present on the regex, causing
+Line 295 
 If /P was present on the regex, causing
  \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 identified substrings that
+ 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
-   Testing Perl-Compatible Regular Expressions
+   PCRE version 2.06 08-Jun-1999
-   PCRE version 0.90 08-Sep-1997
-       re> /^abc(\d+)/
+     re> /^abc(\d+)/
-     data> abc123
+   data> abc123
 : abc123
 : 123
-     data> xyz
+   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
+: cat
++ 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
+: iss
+: ss
+: iss
+: ss
+: ipp
+: 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.
-Line 197 
 following flags has any effect in this c
+Line 349 
 following flags has any effect in this c
  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 (for "information") is given to pcretest, it calls pcre_info()
+ If the option -i is given to pcretest, it is equivalent to adding /I to each
- after compiling an expression, and outputs the information it gets back. If the
+ regular expression: information about the compiled pattern is given after
- pattern is studied, the results of that are also output.
+ compilation.
- If the option -s is given to pcretest, it outputs the size of each compiled
+ If the option -m is given to pcretest, it outputs the size of each compiled
- pattern after it has been 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 2000 times
+ 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
-times and the timing will be distorted.
+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
-Line 216 
 The perltest program
+Line 372 
 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 options.
+ 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
- the testinput file are escaped so that it can be used for perltest as well as
+ testinput1 and testinput3 are escaped so that they can be used for perltest as
- for pcretest, and the special upper case options such as /A that pcretest
+ well as for pcretest, and the special upper case modifiers such as /A that
- recognizes are not used in this file. The output should be identical, apart
+ pcretest recognizes are not used in these files. The output should be
- from the initial identifying banner.
+ identical, apart from the initial identifying banner.
- The testinput2 file is not suitable for feeding to Perltest, since it does
+ The testinput2 and testinput4 files are not suitable for feeding to perltest,
- make use of the special upper case options and escapes that pcretest uses to
+ since they do make use of the special upper case modifiers and escapes that
- test additional features of PCRE.
+ 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.
  Philip Hazel <ph10@cam.ac.uk>
- October 1997
+ June 1999

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