/[pcre]/code/trunk/README

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-revision 33 by nigel,
Sat Feb 24 21:39:01 2007 UTC
+revision 37 by nigel,
Sat Feb 24 21:39:09 2007 UTC
 Line 16 
 README file for PCRE (Perl-compatible re
  * 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
+   Makefile          for building PCRE in Unix systems
    README            this file
-   RunTest           a shell script for running tests
+   RunTest           a Unix shell script for running tests
    Tech.Notes        notes on the encoding
-   pcre.3            man page for the functions
+   pcre.3            man page source for the functions
-   pcreposix.3       man page for the POSIX wrapper API
+   pcre.3.txt        plain text version
+   pcre.3.html       HTML version
+   pcreposix.3       man page source for the POSIX wrapper API
+   pcreposix.3.txt   plain text version
+   pcreposix.3.HTML  HTML version
    dftables.c        auxiliary program for building chartables.c
    get.c             )
    maketables.c      )
-Line 38 
 The distribution should contain the foll
+Line 57 
 The distribution should contain the foll
    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.1           man page source for pgrep
+   pgrep.1.txt       plain text version
+   pgrep.1.HTML      HTML version
    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 testinput
+   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,
+ To build PCRE on a Unix system, first edit Makefile for your system. It is a
- and there are some comments at the top) and then run it. It builds two
+ fairly simple make file, and there are some comments near the top, after the
- libraries called libpcre.a and libpcreposix.a, a test program called pcretest,
+ text "On a Unix system". Then run "make". It builds two libraries called
- and the pgrep command.
+ libpcre.a and libpcreposix.a, a test program called pcretest, and the pgrep
+ command. You can use "make install" to copy these, and the public header file
- To test PCRE, run the RunTest script in the pcre directory. This runs pcretest
+ pcre.h, to appropriate live directories on your system. These installation
- on each of the testinput files in turn, and compares the output with the
+ directories are defined at the top of the Makefile, and you should edit them if
+ necessary.
+ For a non-Unix system, read the comments at the top of Makefile, which give
+ some hints on what needs to be done. PCRE has been compiled on Windows systems
+ and on Macintoshes, but I don't know the details as I don't use those systems.
+ It should be straightforward to build PCRE on any system that has a Standard C
+ compiler.
+ To test PCRE, run the RunTest script in the pcre directory. This can also be
+ run by "make runtest". It runs the pcretest test program (which is documented
+ below) 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).
+ hold the output from pcretest. To run pcretest on just one of the test files,
+ give its number as an argument to RunTest, for example:
- 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
+ script 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.
-Line 88 
 output to say why. If running this test
+Line 118 
 output to say why. If running this test
  in the comparison output, it means that locale is not available on your system,
  despite being listed by "locale". This does not mean that PCRE is broken.
- 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.
- /usr/local/include), and pcre.3 to any suitable man directory (e.g.
- /usr/local/man/man3).
- 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).
  PCRE has its own native API, but a set of "wrapper" functions that are based on
  the POSIX API are also supplied in the library libpcreposix.a. Note that this
  just provides a POSIX calling interface to PCRE: the regular expressions
-Line 112 
 Character tables
+Line 133 
 Character tables
  PCRE uses four tables for manipulating and identifying characters. The final
  argument of the pcre_compile() function is a pointer to a block of memory
- containing the concatenated tables. A call to pcre_maketables() is used to
+ containing the concatenated tables. A call to pcre_maketables() can be used to
- generate a set of tables in the current locale. However, if the final argument
+ generate a set of tables in the current locale. If the final argument for
- is passed as NULL, a set of default tables that is built into the binary is
+ pcre_compile() is passed as NULL, a set of default tables that is built into
- used.
+ the binary is used.
  The source file called chartables.c contains the default set of tables. This is
  not supplied in the distribution, but is built by the program dftables
  (compiled from dftables.c), which uses the ANSI C character handling functions
  such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
- sources. This means that the default C locale set your system will control the
+ sources. This means that the default C locale which is set for your system will
- contents of the tables. You can change the default tables by editing
+ control the contents of these default tables. You can change the default tables
- chartables.c and then re-building PCRE. If you do this, you should probably
+ by editing chartables.c and then re-building PCRE. If you do this, you should
- also edit Makefile to ensure that the file doesn't ever get re-generated.
+ 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
-Line 178 
 example,
+Line 200 
 example,
    /abc/\
- then a backslash is added to the end of the pattern. This provides a way of
+ then a backslash is added to the end of the pattern. This is done to provide a
- testing the error condition that arises if a pattern finishes with a backslash,
+ way of testing the error condition that arises if a pattern finishes with a
- because
+ backslash, because
    /abc\/
-Line 188 
 is interpreted as the first line of a pa
+Line 210 
 is interpreted as the first line of a pa
  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. These
+ PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
- options have the same effect as they do in Perl.
+ example:
- There are also some upper case options that do not match Perl options: /A, /E,
+   /caseless/i
- and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
- The /L option must be followed directly by the name of a locale, for example,
+ 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 option letter. The given locale is set,
+ 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 option, NULL is passed as the tables pointer; that
+ 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 option requests that pcretest output information about the compiled
+ 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 option is a PCRE debugging feature, which also assumes /I. It causes the
+ The /D modifier is a PCRE debugging feature, which also assumes /I. It causes
- internal form of compiled regular expressions to be output after compilation.
+ the internal form of compiled regular expressions to be output after
+ compilation.
- The /S option causes pcre_study() to be called after the expression has been
+ 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 option causes information about the size of memory block used to hold
+ The /M modifier causes the size of memory block used to hold the compiled
- the compile pattern to be output.
+ pattern to be output.
- Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API
+ 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 options except /i and
+ rather than its native API. When this is done, all other modifiers except /i,
- /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
+ /m, and /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is
- is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
+ set if /m is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always,
- PCRE_DOTALL unless REG_NEWLINE is set.
+ 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 246 
 is removed, and it is then scanned for \
+Line 289 
 is removed, and it is then scanned for \
    \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
+   \N     pass the PCRE_NOTEMPTY option to pcre_exec()
    \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 263 
 pcre_exec() returns, starting with numbe
+Line 307 
 pcre_exec() returns, starting with numbe
  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+)/
    data> abc123
 : abc123
 : 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
+: 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
-Line 313 
 The perltest program
+Line 379 
 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. The contents
+ input patterns can be followed only by Perl's lower case modifiers. The
- of testinput1 and testinput3 meet this condition.
+ contents of testinput1 and testinput3 meet this condition.
- The data lines are processed as Perl strings, so if they contain $ or @
+ The data lines are processed as Perl double-quoted strings, so if they contain
- characters, these have to be escaped. For this reason, all such characters in
+ " \ $ or @ characters, these have to be escaped. For this reason, all such
- the testinput file are escaped so that it can be used for perltest as well as
+ characters in testinput1 and testinput3 are escaped so that they can be used
- for pcretest, and the special upper case options such as /A that pcretest
+ for perltest as well as for pcretest, and the special upper case modifiers such
- recognizes are not used in this file. The output should be identical, apart
+ as /A that pcretest recognizes are not used in these files. The output should
- from the initial identifying banner.
+ be identical, apart from the initial identifying banner.
- The testinput2 and testinput4 files are not suitable for feeding to Perltest,
+ The testinput2 and testinput4 files are not suitable for feeding to perltest,
- since they do make use of the special upper case options and escapes that
+ 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.
  Philip Hazel <ph10@cam.ac.uk>
- April 1999
+ July 1999

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