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PCRETEST(1) PCRETEST(1)

NAME
pcretest - a program for testing Perl-compatible regular expressions.

SYNOPSIS

pcretest [options] [source] [destination]

pcretest was written as a test program for the PCRE regular expression library itself, but it can also be used for exper-
imenting with regular expressions. This document describes the features of the test program; for details of the regular
expressions themselves, see the pcrepattern documentation. For details of the PCRE library function calls and their
options, see the pcreapi documentation.

OPTIONS

-b Behave as if each regex has the /B (show bytecode) modifier; the internal form is output after compilation.

-C Output the version number of the PCRE library, and all available information about the optional features that
are included, and then exit.

-d Behave as if each regex has the /D (debug) modifier; the internal form and information about the compiled pat-
tern is output after compilation; -d is equivalent to -b -i.

-dfa Behave as if each data line contains the \D escape sequence; this causes the alternative matching function,
pcre_dfa_exec(), to be used instead of the standard pcre_exec() function (more detail is given below).

-help Output a brief summary these options and then exit.

-i Behave as if each regex has the /I modifier; information about the compiled pattern is given after compilation.

-M Behave as if each data line contains the \M escape sequence; this causes PCRE to discover the minimum
MATCH_LIMIT and MATCH_LIMIT_RECURSION settings by calling pcre_exec() repeatedly with different limits.

-m Output the size of each compiled pattern after it has been compiled. This is equivalent to adding /M to each
regular expression. For compatibility with earlier versions of pcretest, -s is a synonym for -m.

-o osize Set the number of elements in the output vector that is used when calling pcre_exec() or pcre_dfa_exec() to be
osize. The default value is 45, which is enough for 14 capturing subexpressions for pcre_exec() or 22 different
matches for pcre_dfa_exec(). The vector size can be changed for individual matching calls by including \O in
the data line (see below).

-p Behave as if each regex has the /P modifier; the POSIX wrapper API is used to call PCRE. None of the other
options has any effect when -p is set.

-q Do not output the version number of pcretest at the start of execution.

-S size On Unix-like systems, set the size of the runtime stack to size megabytes.

-t Run each compile, study, and match many times with a timer, and output resulting time per compile or match (in
milliseconds). Do not set -m with -t, because you will then get the size output a zillion times, and the timing
will be distorted. You can control the number of iterations that are used for timing by following -t with a
number (as a separate item on the command line). For example, "-t 1000" would iterate 1000 times. The default
is to iterate 500000 times.

-tm This is like -t except that it times only the matching phase, not the compile or study phases.

DESCRIPTION

If pcretest 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, using "re>" to prompt for regular expressions, and "data>" to prompt for data lines.

When pcretest is built, a configuration option can specify that it should be linked with the libreadline library. When
this is done, if the input is from a terminal, it is read using the readline() function. This provides line-editing and
history facilities. The output from the -help option states whether or not readline() will be used.

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.

Each data line is matched separately and independently. If you want to do multi-line matches, you have to use the \n
escape sequence (or \r or \r\n, etc., depending on the newline setting) in a single line of input to encode the newline
sequences. There is no limit on the length of data lines; the input buffer is automatically extended if it is too small.

An empty line signals the end of the data lines, at which point a new regular expression is read. The regular expressions
are given enclosed in any non-alphanumeric 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. 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-alphanumeric,
this does not affect its interpretation. If the terminating delimiter is immediately followed by a backslash, for exam-
ple,

/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 con-
tinuation of the regular expression.

PATTERN MODIFIERS

A pattern may be followed by any number of modifiers, which are mostly single characters. Following Perl usage, these are
referred to below as, for example, "the /i modifier", even though the delimiter of the pattern need not always be a
slash, and no slash is used when writing modifiers. Whitespace may appear between the final pattern delimiter and the
first modifier, and between the modifiers themselves.

The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respec-
tively, when pcre_compile() is called. These four modifier letters have the same effect as they do in Perl. For example:

/caseless/i

The following table shows additional modifiers for setting PCRE compile-time options that do not correspond to anything
in Perl:

/8 PCRE_UTF8
/? PCRE_NO_UTF8_CHECK
/A PCRE_ANCHORED
/C PCRE_AUTO_CALLOUT
/E PCRE_DOLLAR_ENDONLY
/f PCRE_FIRSTLINE
/J PCRE_DUPNAMES
/N PCRE_NO_AUTO_CAPTURE
/U PCRE_UNGREEDY
/W PCRE_UCP
/X PCRE_EXTRA
/<JS> PCRE_JAVASCRIPT_COMPAT
/<cr> PCRE_NEWLINE_CR
/<lf> PCRE_NEWLINE_LF
/<crlf> PCRE_NEWLINE_CRLF
/<anycrlf> PCRE_NEWLINE_ANYCRLF
/<any> PCRE_NEWLINE_ANY
/<bsr_anycrlf> PCRE_BSR_ANYCRLF
/<bsr_unicode> PCRE_BSR_UNICODE

The modifiers that are enclosed in angle brackets are literal strings as shown, including the angle brackets, but the
letters can be in either case. This example sets multiline matching with CRLF as the line ending sequence:

/^abc/m<crlf>

As well as turning on the PCRE_UTF8 option, the /8 modifier also causes any non-printing characters in output strings to
be printed using the \x{hh...} notation if they are valid UTF-8 sequences. Full details of the PCRE options are given in
the pcreapi documentation.

Finding all matches in a string

Searching for all possible matches within each subject string can be requested by the /g or /G modifier. 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 startoffset argument to pcre_exec() to start searching at a new point within the entire string (which is
in effect what Perl does), 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).

If any call to pcre_exec() in a /g or /G sequence matches an empty string, the next call is done with the
PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED flags set in order to search for another, non-empty, match at the same point. If
this second match fails, the start offset is advanced by one character, and the normal match is retried. This imitates
the way Perl handles such cases when using the /g modifier or the split() function.

Other modifiers

There are yet more 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 /B modifier is a debugging feature. It requests that pcretest output a representation of the compiled byte code after
compilation. Normally this information contains length and offset values; however, if /Z is also present, this data is
replaced by spaces. This is a special feature for use in the automatic test scripts; it ensures that the same output is
generated for different internal link sizes.

The /D modifier is a PCRE debugging feature, and is equivalent to /BI, that is, both the /B and the /I modifiers.

The /F modifier causes pcretest to flip the byte order of the fields in the compiled pattern that contain 2-byte and
4-byte numbers. This facility is for testing the feature in PCRE that allows it to execute patterns that were compiled on
a host with a different endianness. This feature is not available when the POSIX interface to PCRE is being used, that
is, when the /P pattern modifier is specified. See also the section about saving and reloading compiled patterns below.

The /I modifier requests that pcretest output information about the compiled pattern (whether it is anchored, has a fixed
first character, and so on). It does this by calling pcre_fullinfo() after compiling a pattern. If the pattern is stud-
ied, the results of that are also output.

The /K modifier requests pcretest to show names from backtracking control verbs that are returned from calls to
pcre_exec(). It causes pcretest to create a pcre_extra block if one has not already been created by a call to
pcre_study(), and to set the PCRE_EXTRA_MARK flag and the mark field within it, every time that pcre_exec() is called. If
the variable that the mark field points to is non-NULL for a match, non-match, or partial match, pcretest prints the
string to which it points. For a match, this is shown on a line by itself, tagged with "MK:". For a non-match it is
added to the message.

The /L modifier must be followed directly by the name of a locale, for example,

/pattern/Lfr_FR

For this reason, it must be the last modifier. 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 (or /T) modifier, NULL is passed as the tables pointer; that is, /L applies only to the expression on which it
appears.

The /M modifier causes the size of memory block used to hold the compiled pattern to be output.

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 /T modifier must be followed by a single digit. It causes a specific set of built-in character tables to be passed to
pcre_compile(). It is used in the standard PCRE tests to check behaviour with different character tables. The digit spec-
ifies the tables as follows:

0 the default ASCII tables, as distributed in
pcre_chartables.c.dist
1 a set of tables defining ISO 8859 characters

In table 1, some characters whose codes are greater than 128 are identified as letters, digits, spaces, etc.

Using the POSIX wrapper API

The /P modifier causes pcretest to call PCRE via the POSIX wrapper API rather than its native API. When /P is set, the
following modifiers set options for the regcomp() function:

/i REG_ICASE
/m REG_NEWLINE
/N REG_NOSUB
/s REG_DOTALL )
/U REG_UNGREEDY ) These options are not part of
/W REG_UCP ) the POSIX standard
/8 REG_UTF8 )

The /+ modifier works as described above. All other modifiers are ignored.

DATA LINES

Before each data line is passed to pcre_exec(), leading and trailing whitespace is removed, and it is then scanned for \
escapes. Some of these are pretty esoteric features, intended for checking out some of the more complicated features of
PCRE. If you are just testing "ordinary" regular expressions, you probably don't need any of these. The following escapes
are recognized:

\a alarm (BEL, \x07)
\b backspace (\x08)
\e escape (\x27)
\f formfeed (\x0c)
\n newline (\x0a)
\qdd set the PCRE_MATCH_LIMIT limit to dd
(any number of digits)
\r carriage return (\x0d)
\t tab (\x09)
\v vertical tab (\x0b)
\nnn octal character (up to 3 octal digits)
\xhh hexadecimal character (up to 2 hex digits)
\x{hh...} hexadecimal character, any number of digits
in UTF-8 mode
\A pass the PCRE_ANCHORED option to pcre_exec()
or pcre_dfa_exec()
\B pass the PCRE_NOTBOL option to pcre_exec()
or pcre_dfa_exec()
\Cdd call pcre_copy_substring() for substring dd
after a successful match (number less than 32)
\Cname call pcre_copy_named_substring() for substring
"name" after a successful match (name termin-
ated by next non alphanumeric character)
\C+ show the current captured substrings at callout
time
\C- do not supply a callout function
\C!n return 1 instead of 0 when callout number n is
reached
\C!n!m return 1 instead of 0 when callout number n is
reached for the nth time
\C*n pass the number n (may be negative) as callout
data; this is used as the callout return value
\D use the pcre_dfa_exec() match function
\F only shortest match for pcre_dfa_exec()
\Gdd call pcre_get_substring() for substring dd
after a successful match (number less than 32)
\Gname call pcre_get_named_substring() for substring
"name" after a successful match (name termin-
ated by next non-alphanumeric character)
\L call pcre_get_substringlist() after a
successful match
\M discover the minimum MATCH_LIMIT and
MATCH_LIMIT_RECURSION settings
\N pass the PCRE_NOTEMPTY option to pcre_exec()
or pcre_dfa_exec(); if used twice, pass the
PCRE_NOTEMPTY_ATSTART option
\Odd set the size of the output vector passed to
pcre_exec() to dd (any number of digits)
\P pass the PCRE_PARTIAL_SOFT option to pcre_exec()
or pcre_dfa_exec(); if used twice, pass the
PCRE_PARTIAL_HARD option
\Qdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
(any number of digits)
\R pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
\S output details of memory get/free calls during matching
\Y pass the PCRE_NO_START_OPTIMIZE option to pcre_exec()
or pcre_dfa_exec()
\Z pass the PCRE_NOTEOL option to pcre_exec()
or pcre_dfa_exec()
\? pass the PCRE_NO_UTF8_CHECK option to
pcre_exec() or pcre_dfa_exec()
\>dd start the match at offset dd (any number of digits);
this sets the startoffset argument for pcre_exec()
or pcre_dfa_exec()
\<cr> pass the PCRE_NEWLINE_CR option to pcre_exec()
or pcre_dfa_exec()
\<lf> pass the PCRE_NEWLINE_LF option to pcre_exec()
or pcre_dfa_exec()
\<crlf> pass the PCRE_NEWLINE_CRLF option to pcre_exec()
or pcre_dfa_exec()
\<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre_exec()
or pcre_dfa_exec()
\<any> pass the PCRE_NEWLINE_ANY option to pcre_exec()
or pcre_dfa_exec()

The escapes that specify line ending sequences are literal strings, exactly as shown. No more than one newline setting
should be present in any data line.

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 \M is present, pcretest calls pcre_exec() several times, with different values in the match_limit and
match_limit_recursion fields of the pcre_extra data structure, until it finds the minimum numbers for each parameter that
allow pcre_exec() to complete. The match_limit number is a measure of the amount of backtracking that takes place, and
checking it out can be instructive. For most simple matches, the number is quite small, but for patterns with very large
numbers of matching possibilities, it can become large very quickly with increasing length of subject string. The
match_limit_recursion number is a measure of how much stack (or, if PCRE is compiled with NO_RECURSE, how much heap) mem-
ory is needed to complete the match attempt.

When \O is used, the value specified may be higher or lower than the size set by the -O command line option (or defaulted
to 45); \O applies only to the call of pcre_exec() for the line in which it appears.

If the /P modifier was present on the pattern, causing the POSIX wrapper API to be used, the only option-setting
sequences that have any effect are \B, \N, and \Z, causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively, to be
passed to regexec().

The use of \x{hh...} to represent UTF-8 characters is not dependent on the use of the /8 modifier on the pattern. It is
recognized always. There may be any number of hexadecimal digits inside the braces. The result is from one to six bytes,
encoded according to the original UTF-8 rules of RFC 2279. This allows for values in the range 0 to 0x7FFFFFFF. Note that
not all of those are valid Unicode code points, or indeed valid UTF-8 characters according to the later rules in RFC
3629.

THE ALTERNATIVE MATCHING FUNCTION

By default, pcretest uses the standard PCRE matching function, pcre_exec() to match each data line. From release 6.0,
PCRE supports an alternative matching function, pcre_dfa_test(), which operates in a different way, and has some restric-
tions. The differences between the two functions are described in the pcrematching documentation.

If a data line contains the \D escape sequence, or if the command line contains the -dfa option, the alternative matching
function is called. This function finds all possible matches at a given point. If, however, the \F escape sequence is
present in the data line, it stops after the first match is found. This is always the shortest possible match.

DEFAULT OUTPUT FROM PCRETEST

This section describes the output when the normal matching function, pcre_exec(), is being used.

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. Otherwise, it outputs "No match" when the return is PCRE_ERROR_NOMATCH,
and "Partial match:" followed by the partially matching substring when pcre_exec() returns PCRE_ERROR_PARTIAL. For any
other returns, it outputs the PCRE negative error number. Here is an example of an interactive pcretest run.

$ pcretest
PCRE version 7.0 30-Nov-2006

re> /^abc(\d+)/
data> abc123
0: abc123
1: 123
data> xyz
No match

Note that unset capturing substrings that are not followed by one that is set are not returned by pcre_exec(), and are
not shown by pcretest. In the following example, there are two capturing substrings, but when the first data line is
matched, the second, unset substring is not shown. An "internal" unset substring is shown as "<unset>", as for the second
data line.

re> /(a)|(b)/
data> a
0: a
1: a
data> b
0: b
1: <unset>
2: b

If the strings contain any non-printing characters, they are output as \0x escapes, or as \x{...} escapes if the /8 modi-
fier was present on the pattern. See below for the definition of non-printing characters. If the pattern has the /+ modi-
fier, 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 the sequences \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 whereas 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 (or \r, \r\n, etc., depending on the newline
sequence setting).

OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION

When the alternative matching function, pcre_dfa_exec(), is used (by means of the \D escape sequence or the -dfa command
line option), the output consists of a list of all the matches that start at the first point in the subject where there
is at least one match. For example:

re> /(tang|tangerine|tan)/
data> yellow tangerine\D
0: tangerine
1: tang
2: tan

(Using the normal matching function on this data finds only "tang".) The longest matching string is always given first
(and numbered zero). After a PCRE_ERROR_PARTIAL return, the output is "Partial match:", followed by the partially match-
ing substring.

If /g is present on the pattern, the search for further matches resumes at the end of the longest match. For example:

re> /(tang|tangerine|tan)/g
data> yellow tangerine and tangy sultana\D
0: tangerine
1: tang
2: tan
0: tang
1: tan
0: tan

Since the matching function does not support substring capture, the escape sequences that are concerned with captured
substrings are not relevant.

RESTARTING AFTER A PARTIAL MATCH

When the alternative matching function has given the PCRE_ERROR_PARTIAL return, indicating that the subject partially
matched the pattern, you can restart the match with additional subject data by means of the \R escape sequence. For exam-
ple:

re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
data> 23ja\P\D
Partial match: 23ja
data> n05\R\D
0: n05

For further information about partial matching, see the pcrepartial documentation.

CALLOUTS

If the pattern contains any callout requests, pcretest's callout function is called during matching. This works with both
matching functions. By default, the called function displays the callout number, the start and current positions in the
text at the callout time, and the next pattern item to be tested. For example, the output

--->pqrabcdef
0 ^ ^ \d

indicates that callout number 0 occurred for a match attempt starting at the fourth character of the subject string, when
the pointer was at the seventh character of the data, and when the next pattern item was \d. Just one circumflex is out-
put if the start and current positions are the same.

Callouts numbered 255 are assumed to be automatic callouts, inserted as a result of the /C pattern modifier. In this
case, instead of showing the callout number, the offset in the pattern, preceded by a plus, is output. For example:

re> /\d?[A-E]\*/C
data> E*
--->E*
+0 ^ \d?
+3 ^ [A-E]
+8 ^^ \*
+10 ^ ^
0: E*

The callout function in pcretest returns zero (carry on matching) by default, but you can use a \C item in a data line
(as described above) to change this.

Inserting callouts can be helpful when using pcretest to check complicated regular expressions. For further information
about callouts, see the pcrecallout documentation.

NON-PRINTING CHARACTERS

When pcretest is outputting text in the compiled version of a pattern, bytes other than 32-126 are always treated as non-
printing characters are are therefore shown as hex escapes.

When pcretest is outputting text that is a matched part of a subject string, it behaves in the same way, unless a differ-
ent locale has been set for the pattern (using the /L modifier). In this case, the isprint() function to distinguish
printing and non-printing characters.

SAVING AND RELOADING COMPILED PATTERNS

The facilities described in this section are not available when the POSIX inteface to PCRE is being used, that is, when
the /P pattern modifier is specified.

When the POSIX interface is not in use, you can cause pcretest to write a compiled pattern to a file, by following the
modifiers with > and a file name. For example:

/pattern/im >/some/file

See the pcreprecompile documentation for a discussion about saving and re-using compiled patterns.

The data that is written is binary. The first eight bytes are the length of the compiled pattern data followed by the
length of the optional study data, each written as four bytes in big-endian order (most significant byte first). If there
is no study data (either the pattern was not studied, or studying did not return any data), the second length is zero.
The lengths are followed by an exact copy of the compiled pattern. If there is additional study data, this follows imme-
diately after the compiled pattern. After writing the file, pcretest expects to read a new pattern.

A saved pattern can be reloaded into pcretest by specifing < and a file name instead of a pattern. The name of the file
must not contain a < character, as otherwise pcretest will interpret the line as a pattern delimited by < characters.
For example:

re> </some/file
Compiled regex loaded from /some/file
No study data

When the pattern has been loaded, pcretest proceeds to read data lines in the usual way.

You can copy a file written by pcretest to a different host and reload it there, even if the new host has opposite endi-
anness to the one on which the pattern was compiled. For example, you can compile on an i86 machine and run on a SPARC
machine.

File names for saving and reloading can be absolute or relative, but note that the shell facility of expanding a file
name that starts with a tilde (~) is not available.

The ability to save and reload files in pcretest is intended for testing and experimentation. It is not intended for pro-
duction use because only a single pattern can be written to a file. Furthermore, there is no facility for supplying cus-
tom character tables for use with a reloaded pattern. If the original pattern was compiled with custom tables, an attempt
to match a subject string using a reloaded pattern is likely to cause pcretest to crash. Finally, if you attempt to load
a file that is not in the correct format, the result is undefined.