srclib/pcre/README

README file for PCRE (Perl-compatible regular expression library)
-----------------------------------------------------------------

The latest release of PCRE is always available from

  ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.gz

Please read the NEWS file if you are upgrading from a previous release.


Building PCRE on a Unix system
------------------------------

To build PCRE on a Unix system, run the "configure" command in the PCRE
distribution directory. This is a standard GNU "autoconf" configuration script,
for which generic instructions are supplied in INSTALL. On many systems just
running "./configure" is sufficient, but the usual methods of changing standard
defaults are available. For example

CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local

specifies that the C compiler should be run with the flags '-O2 -Wall' instead
of the default, and that "make install" should install PCRE under /opt/local
instead of the default /usr/local. The "configure" script builds thre files:

. Makefile is built by copying Makefile.in and making substitutions.
. config.h is built by copying config.in and making substitutions.
. pcre-config is built by copying pcre-config.in and making substitutions.

Once "configure" has run, you can run "make". It builds two libraries called
libpcre and libpcreposix, a test program called pcretest, and the pgrep
command. You can use "make install" to copy these, and the public header file
pcre.h, to appropriate live directories on your system, in the normal way.

Running "make install" also installs the command pcre-config, which can be used
to recall information about the PCRE configuration and installation. For
example,

  pcre-config --version

prints the version number, and

 pcre-config --libs

outputs information about where the library is installed. This command can be
included in makefiles for programs that use PCRE, saving the programmer from
having to remember too many details.


Shared libraries on Unix systems
--------------------------------

The default distribution builds PCRE as two shared libraries. This support is
new and experimental and may not work on all systems. It relies on the
"libtool" scripts - these are distributed with PCRE. It should build a
"libtool" script and use this to compile and link shared libraries, which are
placed in a subdirectory called .libs. The programs pcretest and pgrep are
built to use these uninstalled libraries by means of wrapper scripts. When you
use "make install" to install shared libraries, pgrep and pcretest are
automatically re-built to use the newly installed libraries. However, only
pgrep is installed, as pcretest is really just a test program.

To build PCRE using static libraries you must use --disable-shared when
configuring it. For example

./configure --prefix=/usr/gnu --disable-shared

Then run "make" in the usual way.


Building on non-Unix systems
----------------------------

For a non-Unix system, read the comments in the file NON-UNIX-USE. PCRE has
been compiled on Windows systems and on Macintoshes, but I don't know the
details because I don't use those systems. It should be straightforward to
build PCRE on any system that has a Standard C compiler, because it uses only
Standard C functions.


Testing PCRE
------------

To test PCRE on a Unix system, run the RunTest script in the pcre directory.
(This can also be run by "make runtest" or "make check".) For other systems,
see the instruction in NON-UNIX-USE.

The script runs the pcretest test program (which is documented in
doc/pcretest.txt) on each of the testinput files (in the testdata directory) 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. 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
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.

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"

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.

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
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.


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() can be used to
generate a set of tables in the current locale. If the final argument for
pcre_compile() is passed as NULL, a set of default tables that is built into
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 which is set for your system will
control the contents of these default tables. You can change the default tables
by editing chartables.c and then re-building PCRE. If you do this, you should
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 final 256-byte table has bits indicating various character types, as
follows:

    1   white space character
    2   letter
    4   decimal digit
    8   hexadecimal digit
   16   alphanumeric or '_'
  128   regular expression metacharacter or binary zero

You should not alter the set of characters that contain the 128 bit, as that
will cause PCRE to malfunction.


Manifest
--------

The distribution should contain the following files:

(A) The actual source files of the PCRE library functions and their
    headers:

  dftables.c            auxiliary program for building chartables.c
  get.c                 )
  maketables.c          )
  study.c               ) source of
  pcre.c                )   the functions
  pcreposix.c           )
  pcre.in               "source" for the header for the external API; pcre.h
                          is built from this by "configure"
  pcreposix.h           header for the external POSIX wrapper API
  internal.h            header for internal use
  config.in             template for config.h, which is built by configure

(B) Auxiliary files:

  AUTHORS               information about the author of PCRE
  ChangeLog             log of changes to the code
  INSTALL               generic installation instructions
  LICENCE               conditions for the use of PCRE
  COPYING               the same, using GNU's standard name
  Makefile.in           template for Unix Makefile, which is built by configure
  NEWS                  important changes in this release
  NON-UNIX-USE          notes on building PCRE on non-Unix systems
  README                this file
  RunTest               a Unix shell script for running tests
  config.guess          ) files used by libtool,
  config.sub            )   used only when building a shared library
  configure             a configuring shell script (built by autoconf)
  configure.in          the autoconf input used to build configure
  doc/Tech.Notes        notes on the encoding
  doc/pcre.3            man page source for the PCRE functions
  doc/pcre.html         HTML version
  doc/pcre.txt          plain text version
  doc/pcreposix.3       man page source for the POSIX wrapper API
  doc/pcreposix.html    HTML version
  doc/pcreposix.txt     plain text version
  doc/pcretest.txt      documentation of test program
  doc/perltest.txt      documentation of Perl test program
  doc/pgrep.1           man page source for the pgrep utility
  doc/pgrep.html        HTML version
  doc/pgrep.txt         plain text version
  install-sh            a shell script for installing files
  ltconfig              ) files used to build "libtool",
  ltmain.sh             )   used only when building a shared library
  pcretest.c            test program
  perltest              Perl test program
  pgrep.c               source of a grep utility that uses PCRE
  pcre-config.in        source of script which retains PCRE information
  testdata/testinput1   test data, compatible with Perl 5.004 and 5.005
  testdata/testinput2   test data for error messages and non-Perl things
  testdata/testinput3   test data, compatible with Perl 5.005
  testdata/testinput4   test data for locale-specific tests
  testdata/testoutput1  test results corresponding to testinput1
  testdata/testoutput2  test results corresponding to testinput2
  testdata/testoutput3  test results corresponding to testinput3
  testdata/testoutput4  test results corresponding to testinput4

(C) Auxiliary files for Win32 DLL

  dll.mk
  pcre.def

Philip Hazel <ph10@cam.ac.uk>
February 2000