Contents of /code/trunk/README

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
  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.

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.

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
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.


The pcretest program
--------------------

This program is intended for testing PCRE, but it can also be used for
experimenting with regular expressions.

If it is given two filename arguments, it reads from the first and writes to
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/\

then a backslash is added to the end of the pattern. This is done to provide a
way of testing the error condition that arises if a pattern finishes with a
backslash, because

  /abc\/

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:

  \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.

Philip Hazel <ph10@cam.ac.uk>
June 1999
1	nigel	3	README file for PCRE (Perl-compatible regular expressions)
2			----------------------------------------------------------
3
4	nigel	23	*******************************************************************************
5			* IMPORTANT FOR THOSE UPGRADING FROM VERSIONS BEFORE 2.00 *
6			* *
7			* Please note that there has been a change in the API such that a larger *
8			* ovector is required at matching time, to provide some additional workspace. *
9			* The new man page has details. This change was necessary in order to support *
10			* some of the new functionality in Perl 5.005. *
11	nigel	25	* *
12			* IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.00 *
13			* *
14			* Another (I hope this is the last!) change has been made to the API for the *
15			* pcre_compile() function. An additional argument has been added to make it *
16			* possible to pass over a pointer to character tables built in the current *
17			* locale by pcre_maketables(). To use the default tables, this new arguement *
18			* should be passed as NULL. *
19	nigel	35	* *
20			* IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.05 *
21			* *
22			* Yet another (and again I hope this really is the last) change has been made *
23			* to the API for the pcre_exec() function. An additional argument has been *
24			* added to make it possible to start the match other than at the start of the *
25			* subject string. This is important if there are lookbehinds. The new man *
26			* page has the details, but you just want to convert existing programs, all *
27			* you need to do is to stick in a new fifth argument to pcre_exec(), with a *
28			* value of zero. For example, change *
29			* *
30			* pcre_exec(pattern, extra, subject, length, options, ovec, ovecsize) *
31			* to *
32			* pcre_exec(pattern, extra, subject, length, 0, options, ovec, ovecsize) *
33	nigel	23	*******************************************************************************
34
35	nigel	35
36	nigel	3	The distribution should contain the following files:
37
38			ChangeLog log of changes to the code
39	nigel	29	LICENCE conditions for the use of PCRE
40	nigel	3	Makefile for building PCRE
41			README this file
42	nigel	23	RunTest a shell script for running tests
43	nigel	3	Tech.Notes notes on the encoding
44			pcre.3 man page for the functions
45			pcreposix.3 man page for the POSIX wrapper API
46	nigel	27	dftables.c auxiliary program for building chartables.c
47	nigel	29	get.c )
48	nigel	25	maketables.c )
49	nigel	3	study.c ) source of
50			pcre.c ) the functions
51			pcreposix.c )
52			pcre.h header for the external API
53			pcreposix.h header for the external POSIX wrapper API
54			internal.h header for internal use
55			pcretest.c test program
56			pgrep.1 man page for pgrep
57			pgrep.c source of a grep utility that uses PCRE
58			perltest Perl test program
59	nigel	33	testinput1 test data, compatible with Perl 5.004 and 5.005
60	nigel	3	testinput2 test data for error messages and non-Perl things
61	nigel	23	testinput3 test data, compatible with Perl 5.005
62	nigel	25	testinput4 test data for locale-specific tests
63	nigel	35	testoutput1 test results corresponding to testinput1
64	nigel	3	testoutput2 test results corresponding to testinput2
65	nigel	25	testoutput3 test results corresponding to testinput3
66			testoutput4 test results corresponding to testinput4
67	nigel	3
68	nigel	23	To build PCRE, edit Makefile for your system (it is a fairly simple make file,
69			and there are some comments at the top) and then run it. It builds two
70			libraries called libpcre.a and libpcreposix.a, a test program called pcretest,
71			and the pgrep command.
72	nigel	3
73	nigel	23	To test PCRE, run the RunTest script in the pcre directory. This runs pcretest
74			on each of the testinput files in turn, and compares the output with the
75			contents of the corresponding testoutput file. A file called testtry is used to
76			hold the output from pcretest (which is documented below).
77	nigel	3
78	nigel	23	To run pcretest on just one of the test files, give its number as an argument
79			to RunTest, for example:
80	nigel	3
81	nigel	23	RunTest 3
82	nigel	3
83	nigel	23	The first and third test files can also be fed directly into the perltest
84			program to check that Perl gives the same results. The third file requires the
85			additional features of release 5.005, which is why it is kept separate from the
86			main test input, which needs only Perl 5.004. In the long run, when 5.005 is
87			widespread, these two test files may get amalgamated.
88	nigel	3
89	nigel	29	The second set of tests check pcre_info(), pcre_study(), pcre_copy_substring(),
90			pcre_get_substring(), pcre_get_substring_list(), error detection and run-time
91			flags that are specific to PCRE, as well as the POSIX wrapper API.
92	nigel	7
93	nigel	25	The fourth set of tests checks pcre_maketables(), the facility for building a
94			set of character tables for a specific locale and using them instead of the
95			default tables. The tests make use of the "fr" (French) locale. Before running
96			the test, the script checks for the presence of this locale by running the
97			"locale" command. If that command fails, or if it doesn't include "fr" in the
98			list of available locales, the fourth test cannot be run, and a comment is
99			output to say why. If running this test produces instances of the error
100
101			** Failed to set locale "fr"
102
103			in the comparison output, it means that locale is not available on your system,
104			despite being listed by "locale". This does not mean that PCRE is broken.
105
106	nigel	3	To install PCRE, copy libpcre.a to any suitable library directory (e.g.
107			/usr/local/lib), pcre.h to any suitable include directory (e.g.
108			/usr/local/include), and pcre.3 to any suitable man directory (e.g.
109			/usr/local/man/man3).
110
111			To install the pgrep command, copy it to any suitable binary directory, (e.g.
112			/usr/local/bin) and pgrep.1 to any suitable man directory (e.g.
113			/usr/local/man/man1).
114
115			PCRE has its own native API, but a set of "wrapper" functions that are based on
116			the POSIX API are also supplied in the library libpcreposix.a. Note that this
117			just provides a POSIX calling interface to PCRE: the regular expressions
118			themselves still follow Perl syntax and semantics. The header file
119			for the POSIX-style functions is called pcreposix.h. The official POSIX name is
120			regex.h, but I didn't want to risk possible problems with existing files of
121			that name by distributing it that way. To use it with an existing program that
122	nigel	23	uses the POSIX API, it will have to be renamed or pointed at by a link.
123	nigel	3
124
125			Character tables
126			----------------
127
128	nigel	25	PCRE uses four tables for manipulating and identifying characters. The final
129			argument of the pcre_compile() function is a pointer to a block of memory
130	nigel	35	containing the concatenated tables. A call to pcre_maketables() can be used to
131			generate a set of tables in the current locale. If the final argument for
132			pcre_compile() is passed as NULL, a set of default tables that is built into
133			the binary is used.
134	nigel	3
135	nigel	25	The source file called chartables.c contains the default set of tables. This is
136	nigel	27	not supplied in the distribution, but is built by the program dftables
137			(compiled from dftables.c), which uses the ANSI C character handling functions
138	nigel	25	such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
139	nigel	35	sources. This means that the default C locale which is set for your system will
140			control the contents of these default tables. You can change the default tables
141			by editing chartables.c and then re-building PCRE. If you do this, you should
142			probably also edit Makefile to ensure that the file doesn't ever get
143			re-generated.
144	nigel	3
145	nigel	25	The first two 256-byte tables provide lower casing and case flipping functions,
146			respectively. The next table consists of three 32-byte bit maps which identify
147			digits, "word" characters, and white space, respectively. These are used when
148			building 32-byte bit maps that represent character classes.
149
150			The final 256-byte table has bits indicating various character types, as
151	nigel	3	follows:
152
153			1 white space character
154			2 letter
155			4 decimal digit
156			8 hexadecimal digit
157			16 alphanumeric or '_'
158			128 regular expression metacharacter or binary zero
159
160			You should not alter the set of characters that contain the 128 bit, as that
161			will cause PCRE to malfunction.
162
163
164			The pcretest program
165			--------------------
166
167			This program is intended for testing PCRE, but it can also be used for
168			experimenting with regular expressions.
169
170			If it is given two filename arguments, it reads from the first and writes to
171			the second. If it is given only one filename argument, it reads from that file
172			and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
173			prompts for each line of input.
174
175			The program handles any number of sets of input on a single input file. Each
176			set starts with a regular expression, and continues with any number of data
177			lines to be matched against the pattern. An empty line signals the end of the
178			set. The regular expressions are given enclosed in any non-alphameric
179	nigel	29	delimiters other than backslash, for example
180	nigel	3
181			/(a\|bc)x+yz/
182
183	nigel	29	White space before the initial delimiter is ignored. A regular expression may
184			be continued over several input lines, in which case the newline characters are
185			included within it. See the testinput files for many examples. It is possible
186			to include the delimiter within the pattern by escaping it, for example
187	nigel	3
188	nigel	29	/abc\/def/
189
190			If you do so, the escape and the delimiter form part of the pattern, but since
191			delimiters are always non-alphameric, this does not affect its interpretation.
192			If the terminating delimiter is immediately followed by a backslash, for
193			example,
194
195			/abc/\
196
197	nigel	35	then a backslash is added to the end of the pattern. This is done to provide a
198			way of testing the error condition that arises if a pattern finishes with a
199			backslash, because
200	nigel	29
201			/abc\/
202
203			is interpreted as the first line of a pattern that starts with "abc/", causing
204			pcretest to read the next line as a continuation of the regular expression.
205
206			The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,
207	nigel	35	PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
208			example:
209	nigel	29
210	nigel	35	/caseless/i
211	nigel	3
212	nigel	35	These modifier letters have the same effect as they do in Perl. There are
213			others which set PCRE options that do not correspond to anything in Perl: /A,
214			/E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
215	nigel	25
216	nigel	35	Searching for all possible matches within each subject string can be requested
217			by the /g or /G modifier. The /g modifier behaves similarly to the way it does
218			in Perl. After finding a match, PCRE is called again to search the remainder of
219			the subject string. The difference between /g and /G is that the former uses
220			the start_offset argument to pcre_exec() to start searching at a new point
221			within the entire string, whereas the latter passes over a shortened substring.
222			This makes a difference to the matching process if the pattern begins with a
223			lookbehind assertion (including \b or \B).
224
225			There are a number of other modifiers for controlling the way pcretest
226			operates.
227
228			The /+ modifier requests that as well as outputting the substring that matched
229			the entire pattern, pcretest should in addition output the remainder of the
230			subject string. This is useful for tests where the subject contains multiple
231			copies of the same substring.
232
233			The /L modifier must be followed directly by the name of a locale, for example,
234
235	nigel	25	/pattern/Lfr
236
237	nigel	35	For this reason, it must be the last modifier letter. The given locale is set,
238	nigel	25	pcre_maketables() is called to build a set of character tables for the locale,
239			and this is then passed to pcre_compile() when compiling the regular
240	nigel	35	expression. Without an /L modifier, NULL is passed as the tables pointer; that
241	nigel	25	is, /L applies only to the expression on which it appears.
242
243	nigel	35	The /I modifier requests that pcretest output information about the compiled
244	nigel	25	expression (whether it is anchored, has a fixed first character, and so on). It
245			does this by calling pcre_info() after compiling an expression, and outputting
246			the information it gets back. If the pattern is studied, the results of that
247			are also output.
248
249	nigel	35	The /D modifier is a PCRE debugging feature, which also assumes /I. It causes
250			the internal form of compiled regular expressions to be output after
251			compilation.
252	nigel	25
253	nigel	35	The /S modifier causes pcre_study() to be called after the expression has been
254	nigel	25	compiled, and the results used when the expression is matched.
255
256	nigel	35	The /M modifier causes information about the size of memory block used to hold
257	nigel	31	the compile pattern to be output.
258
259	nigel	35	Finally, the /P modifier causes pcretest to call PCRE via the POSIX wrapper API
260			rather than its native API. When this is done, all other modifiers except /i,
261			/m, and /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is
262			set if /m is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always,
263			and PCRE_DOTALL unless REG_NEWLINE is set.
264	nigel	3
265			Before each data line is passed to pcre_exec(), leading and trailing whitespace
266			is removed, and it is then scanned for \ escapes. The following are recognized:
267
268			\a alarm (= BEL)
269			\b backspace
270			\e escape
271			\f formfeed
272			\n newline
273			\r carriage return
274			\t tab
275			\v vertical tab
276			\nnn octal character (up to 3 octal digits)
277			\xhh hexadecimal character (up to 2 hex digits)
278
279			\A pass the PCRE_ANCHORED option to pcre_exec()
280			\B pass the PCRE_NOTBOL option to pcre_exec()
281	nigel	29	\Cdd call pcre_copy_substring() for substring dd after a successful match
282			(any decimal number less than 32)
283			\Gdd call pcre_get_substring() for substring dd after a successful match
284			(any decimal number less than 32)
285			\L call pcre_get_substringlist() after a successful match
286	nigel	3	\Odd set the size of the output vector passed to pcre_exec() to dd
287			(any number of decimal digits)
288			\Z pass the PCRE_NOTEOL option to pcre_exec()
289
290			A backslash followed by anything else just escapes the anything else. If the
291			very last character is a backslash, it is ignored. This gives a way of passing
292			an empty line as data, since a real empty line terminates the data input.
293
294			If /P was present on the regex, causing the POSIX wrapper API to be used, only
295			\B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
296			regexec() respectively.
297
298	nigel	29	When a match succeeds, pcretest outputs the list of captured substrings that
299	nigel	3	pcre_exec() returns, starting with number 0 for the string that matched the
300			whole pattern. Here is an example of an interactive pcretest run.
301
302			$ pcretest
303	nigel	35	PCRE version 2.06 08-Jun-1999
304	nigel	3
305	nigel	23	re> /^abc(\d+)/
306			data> abc123
307	nigel	35	0: abc123
308			1: 123
309	nigel	23	data> xyz
310	nigel	3	No match
311
312	nigel	35	If the strings contain any non-printing characters, they are output as \0x
313			escapes. If the pattern has the /+ modifier, then the output for substring 0 is
314			followed by the the rest of the subject string, identified by "0+" like this:
315
316			re> /cat/+
317			data> cataract
318			0: cat
319			0+ aract
320
321			If the pattern has the /g or /G modifier, the results of successive matching
322			attempts are output in sequence, like this:
323
324			re> /\Bi(\w\w)/g
325			data> Mississippi
326			0: iss
327			1: ss
328			0: iss
329			1: ss
330			0: ipp
331			1: pp
332
333			"No match" is output only if the first match attempt fails.
334
335	nigel	29	If any of \C, \G, or \L are present in a data line that is successfully
336			matched, the substrings extracted by the convenience functions are output with
337			C, G, or L after the string number instead of a colon. This is in addition to
338			the normal full list. The string length (that is, the return from the
339			extraction function) is given in parentheses after each string for \C and \G.
340
341	nigel	3	Note that while patterns can be continued over several lines (a plain ">"
342			prompt is used for continuations), data lines may not. However newlines can be
343			included in data by means of the \n escape.
344
345			If the -p option is given to pcretest, it is equivalent to adding /P to each
346			regular expression: the POSIX wrapper API is used to call PCRE. None of the
347			following flags has any effect in this case.
348
349			If the option -d is given to pcretest, it is equivalent to adding /D to each
350			regular expression: the internal form is output after compilation.
351
352	nigel	25	If the option -i is given to pcretest, it is equivalent to adding /I to each
353			regular expression: information about the compiled pattern is given after
354			compilation.
355	nigel	3
356	nigel	31	If the option -m is given to pcretest, it outputs the size of each compiled
357			pattern after it has been compiled. It is equivalent to adding /M to each
358			regular expression. For compatibility with earlier versions of pcretest, -s is
359			a synonym for -m.
360	nigel	3
361	nigel	29	If the -t option is given, each compile, study, and match is run 20000 times
362	nigel	3	while being timed, and the resulting time per compile or match is output in
363			milliseconds. Do not set -t with -s, because you will then get the size output
364	nigel	29	20000 times and the timing will be distorted. If you want to change the number
365	nigel	23	of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
366			pcretest.c
367	nigel	3
368
369
370			The perltest program
371			--------------------
372
373			The perltest program tests Perl's regular expressions; it has the same
374			specification as pcretest, and so can be given identical input, except that
375	nigel	35	input patterns can be followed only by Perl's lower case modifiers. The
376			contents of testinput1 and testinput3 meet this condition.
377	nigel	3
378			The data lines are processed as Perl strings, so if they contain $ or @
379			characters, these have to be escaped. For this reason, all such characters in
380	nigel	35	testinput1 and testinput3 are escaped so that they can be used for perltest as
381			well as for pcretest, and the special upper case modifiers such as /A that
382			pcretest recognizes are not used in these files. The output should be
383			identical, apart from the initial identifying banner.
384	nigel	3
385	nigel	35	The testinput2 and testinput4 files are not suitable for feeding to perltest,
386			since they do make use of the special upper case modifiers and escapes that
387	nigel	25	pcretest uses to test some features of PCRE. The first of these files also
388			contains malformed regular expressions, in order to check that PCRE diagnoses
389			them correctly.
390	nigel	3
391			Philip Hazel <ph10@cam.ac.uk>
392	nigel	35	June 1999