pcre2pattern
documentation. For details of the PCRE2 library function calls and their options, see the HREF
pcre2api
documentation.
The input for pcre2test is a sequence of regular expression patterns and subject strings to be matched. There are also command lines for setting defaults and controlling some special actions. The output shows the result of each match attempt. Modifiers on external or internal command lines, the patterns, and the subject lines specify PCRE2 function options, control how the subject is processed, and what output is produced.
As the original fairly simple PCRE library evolved, it acquired many different features, and as a result, the original pcretest program ended up with a lot of options in a messy, arcane syntax for testing all the features. The move to the new PCRE2 API provided an opportunity to re-implement the test program as pcre2test, with a cleaner modifier syntax. Nevertheless, there are still many obscure modifiers, some of which are specifically designed for use in conjunction with the test script and data files that are distributed as part of PCRE2. All the modifiers are documented here, some without much justification, but many of them are unlikely to be of use except when testing the libraries. . .
In the rest of this document, the names of library functions and structures
are given in generic form, for example, pcre_compile(). The actual
names used in the libraries have a suffix _8, _16, or _32, as appropriate.
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.
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The input is processed using using C's string functions, so must not contain binary zeros, even though in Unix-like environments, fgets() treats any bytes other than newline as data characters. An error is generated if a binary zero is encountered. By default subject lines are processed for backslash escapes, which makes it possible to include any data value in strings that are passed to the library for matching. For patterns, there is a facility for specifying some or all of the 8-bit input characters as hexadecimal pairs, which makes it possible to include binary zeros. . .
</a>
"Setting compilation options"
below) is set, the pattern and any following subject lines are interpreted as UTF-8 strings and translated to UTF-16 or UTF-32 as appropriate.
For non-UTF testing of wide characters, the utf8_input modifier can be used. This is mutually exclusive with utf, and is allowed only in 16-bit or 32-bit mode. It causes the pattern and following subject lines to be treated as UTF-8 according to the original definition (RFC 2279), which allows for character values up to 0x7fffffff. Each character is placed in one 16-bit or 32-bit code unit (in the 16-bit case, values greater than 0xffff cause an error to occur).
UTF-8 (in its original definition) is not capable of encoding values greater than 0x7fffffff, but such values can be handled by the 32-bit library. When testing this library in non-UTF mode with utf8_input set, if any character is preceded by the byte 0xff (which is an invalid byte in UTF-8) 0x80000000 is added to the character's value. This is the only way of passing such code points in a pattern string. For subject strings, using an escape sequence is preferable. . .
10 -8 If the 8-bit library has been built, this option causes it to be used (this is the default). If the 8-bit library has not been built, this option causes an error.
10 -16 If the 16-bit library has been built, this option causes it to be used. If only the 16-bit library has been built, this is the default. If the 16-bit library has not been built, this option causes an error.
10 -32 If the 32-bit library has been built, this option causes it to be used. If only the 32-bit library has been built, this is the default. If the 32-bit library has not been built, this option causes an error.
10 -ac Behave as if each pattern has the auto_callout modifier, that is, insert automatic callouts into every pattern that is compiled.
10 -AC As for -ac, but in addition behave as if each subject line has the callout_extra modifier, that is, show additional information from callouts.
10 -b Behave as if each pattern has the fullbincode modifier; the full internal binary form of the pattern is output after compilation.
10 -C Output the version number of the PCRE2 library, and all available information about the optional features that are included, and then exit with zero exit code. All other options are ignored. If both -C and -LM are present, whichever is first is recognized.
10 -C option Output information about a specific build-time option, then exit. This functionality is intended for use in scripts such as RunTest. The following options output the value and set the exit code as indicated: ebcdic-nl the code for LF (= NL) in an EBCDIC environment: 0x15 or 0x25 0 if used in an ASCII environment exit code is always 0 linksize the configured internal link size (2, 3, or 4) exit code is set to the link size newline the default newline setting: CR, LF, CRLF, ANYCRLF, ANY, or NUL exit code is always 0 bsr the default setting for what \eR matches: ANYCRLF or ANY exit code is always 0 The following options output 1 for true or 0 for false, and set the exit code to the same value: backslash-C \eC is supported (not locked out) ebcdic compiled for an EBCDIC environment jit just-in-time support is available pcre2-16 the 16-bit library was built pcre2-32 the 32-bit library was built pcre2-8 the 8-bit library was built unicode Unicode support is available If an unknown option is given, an error message is output; the exit code is 0.
10 -d Behave as if each pattern has the debug modifier; the internal form and information about the compiled pattern is output after compilation; -d is equivalent to -b -i.
10 -dfa Behave as if each subject line has the dfa modifier; matching is done using the pcre2_dfa_match() function instead of the default pcre2_match().
10 -error number[,number,...] Call pcre2_get_error_message() for each of the error numbers in the comma-separated list, display the resulting messages on the standard output, then exit with zero exit code. The numbers may be positive or negative. This is a convenience facility for PCRE2 maintainers.
10 -help Output a brief summary these options and then exit.
10 -i Behave as if each pattern has the info modifier; information about the compiled pattern is given after compilation.
10 -jit Behave as if each pattern line has the jit modifier; after successful compilation, each pattern is passed to the just-in-time compiler, if available.
10 -jitverify Behave as if each pattern line has the jitverify modifier; after successful compilation, each pattern is passed to the just-in-time compiler, if available, and the use of JIT is verified.
10 -LM List modifiers: write a list of available pattern and subject modifiers to the standard output, then exit with zero exit code. All other options are ignored. If both -C and -LM are present, whichever is first is recognized.
10 -pattern modifier-list Behave as if each pattern line contains the given modifiers.
10 -q Do not output the version number of pcre2test at the start of execution.
10 -S size On Unix-like systems, set the size of the run-time stack to size mebibytes (units of 1024*1024 bytes).
10 -subject modifier-list Behave as if each subject line contains the given modifiers.
10 -t Run each compile and match many times with a timer, and output the resulting times per compile or match. When JIT is used, separate times are given for the initial compile and the JIT compile. 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" iterates 1000 times. The default is to iterate 500,000 times.
10 -tm This is like -t except that it times only the matching phase, not the compile phase.
10 -T -TM These behave like -t and -tm, but in addition, at the end of a run, the total times for all compiles and matches are output.
10 -version Output the PCRE2 version number and then exit. . .
When pcre2test is built, a configuration option can specify that it should be linked with the libreadline or libedit 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 tests, each of which consists of a set of input lines. Each set starts with a regular expression pattern, followed by any number of subject lines to be matched against that pattern. In between sets of test data, command lines that begin with # may appear. This file format, with some restrictions, can also be processed by the perltest.sh script that is distributed with PCRE2 as a means of checking that the behaviour of PCRE2 and Perl is the same. For a specification of perltest.sh, see the comments near its beginning.
When the input is a terminal, pcre2test prompts for each line of input, using "re>" to prompt for regular expression patterns, and "data>" to prompt for subject lines. Command lines starting with # can be entered only in response to the "re>" prompt.
Each subject line is matched separately and independently. If you want to do multi-line matches, you have to use the \en escape sequence (or \er or \er\en, 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 subject lines; the input buffer is automatically extended if it is too small. There are replication features that makes it possible to generate long repetitive pattern or subject lines without having to supply them explicitly.
An empty line or the end of the file signals the end of the subject lines for a test, at which point a new pattern or command line is expected if there is still input to be read. . .
This is a trigger guard that is used in test files to ensure that UTF or
Unicode property tests are not accidentally added to files that are used when
Unicode support is not included in the library. Setting PCRE2_NEVER_UTF and
PCRE2_NEVER_UCP as a default can also be obtained by the use of #pattern;
the difference is that #forbid_utf cannot be unset, and the automatic
options are not displayed in pattern information, to avoid cluttering up test
output.
#load <filename>
This command is used to load a set of precompiled patterns from a file, as
described in the section entitled "Saving and restoring compiled patterns"
HTML <a href="#saverestore">
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below.
#newline_default [<newline-list>]
When PCRE2 is built, a default newline convention can be specified. This
determines which characters and/or character pairs are recognized as indicating
a newline in a pattern or subject string. The default can be overridden when a
pattern is compiled. The standard test files contain tests of various newline
conventions, but the majority of the tests expect a single linefeed to be
recognized as a newline by default. Without special action the tests would fail
when PCRE2 is compiled with either CR or CRLF as the default newline.
The #newline_default command specifies a list of newline types that are acceptable as the default. The types must be one of CR, LF, CRLF, ANYCRLF, ANY, or NUL (in upper or lower case), for example: #newline_default LF Any anyCRLF If the default newline is in the list, this command has no effect. Otherwise, except when testing the POSIX API, a newline modifier that specifies the first newline convention in the list (LF in the above example) is added to any pattern that does not already have a newline modifier. If the newline list is empty, the feature is turned off. This command is present in a number of the standard test input files.
When the POSIX API is being tested there is no way to override the default
newline convention, though it is possible to set the newline convention from
within the pattern. A warning is given if the posix or posix_nosub
modifier is used when #newline_default would set a default for the
non-POSIX API.
#pattern <modifier-list>
This command sets a default modifier list that applies to all subsequent
patterns. Modifiers on a pattern can change these settings.
#perltest
The appearance of this line causes all subsequent modifier settings to be
checked for compatibility with the perltest.sh script, which is used to
confirm that Perl gives the same results as PCRE2. Also, apart from comment
lines, #pattern commands, and #subject commands that set or unset "mark", no
command lines are permitted, because they and many of the modifiers are
specific to pcre2test, and should not be used in test files that are also
processed by perltest.sh. The #perltest command helps detect tests
that are accidentally put in the wrong file.
#pop [<modifiers>]
#popcopy [<modifiers>]
These commands are used to manipulate the stack of compiled patterns, as
described in the section entitled "Saving and restoring compiled patterns"
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</a>
below.
#save <filename>
This command is used to save a set of compiled patterns to a file, as described
in the section entitled "Saving and restoring compiled patterns"
HTML <a href="#saverestore">
</a>
below.
#subject <modifier-list>
This command sets a default modifier list that applies to all subsequent
subject lines. Modifiers on a subject line can change these settings.
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A few of the more common modifiers can also be specified as single letters, for example "i" for "caseless". In documentation, following the Perl convention, these are written with a slash ("the /i modifier") for clarity. Abbreviated modifiers must all be concatenated in the first item of a modifier list. If the first item is not recognized as a long modifier name, it is interpreted as a sequence of these abbreviations. For example: /abc/ig,newline=cr,jit=3 This is a pattern line whose modifier list starts with two one-letter modifiers (/i and /g). The lower-case abbreviated modifiers are the same as used in Perl. . .
A pattern can be followed by a modifier list (details below). . .
Note that \exhh specifies one byte rather than one character in UTF-8 mode; this makes it possible to construct invalid UTF-8 sequences for testing purposes. On the other hand, \ex{hh} is interpreted as a UTF-8 character in UTF-8 mode, generating more than one byte if the value is greater than 127. When testing the 8-bit library not in UTF-8 mode, \ex{hh} generates one byte for values less than 256, and causes an error for greater values.
In UTF-16 mode, all 4-digit \ex{hhhh} values are accepted. This makes it possible to construct invalid UTF-16 sequences for testing purposes.
In UTF-32 mode, all 4- to 8-digit \ex{...} values are accepted. This makes it possible to construct invalid UTF-32 sequences for testing purposes.
There is a special backslash sequence that specifies replication of one or more characters: \e[<characters>]{<count>} This makes it possible to test long strings without having to provide them as part of the file. For example: \e[abc]{4} is converted to "abcabcabcabc". This feature does not support nesting. To include a closing square bracket in the characters, code it as \ex5D.
A backslash followed by an equals sign marks the end of the subject string and the start of a modifier list. For example: abc\e=notbol,notempty If the subject string is empty and \e= is followed by whitespace, the line is treated as a comment line, and is not used for matching. For example: \e= This is a comment. abc\e= This is an invalid modifier list. A backslash followed by any other non-alphanumeric character just escapes that character. A backslash followed by anything else causes an error. However, if the very last character in the line is a backslash (and there is no modifier list), it is ignored. This gives a way of passing an empty line as data, since a real empty line terminates the data input.
If the subject_literal modifier is set for a pattern, all subject lines that follow are treated as literals, with no special treatment of backslashes. No replication is possible, and any subject modifiers must be set as defaults by a #subject command. . .
pcre2api
for a description of the effects of these options. allow_empty_class set PCRE2_ALLOW_EMPTY_CLASS allow_surrogate_escapes set PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES alt_bsux set PCRE2_ALT_BSUX alt_circumflex set PCRE2_ALT_CIRCUMFLEX alt_verbnames set PCRE2_ALT_VERBNAMES anchored set PCRE2_ANCHORED auto_callout set PCRE2_AUTO_CALLOUT bad_escape_is_literal set PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL /i caseless set PCRE2_CASELESS dollar_endonly set PCRE2_DOLLAR_ENDONLY /s dotall set PCRE2_DOTALL dupnames set PCRE2_DUPNAMES endanchored set PCRE2_ENDANCHORED /x extended set PCRE2_EXTENDED /xx extended_more set PCRE2_EXTENDED_MORE firstline set PCRE2_FIRSTLINE literal set PCRE2_LITERAL match_line set PCRE2_EXTRA_MATCH_LINE match_unset_backref set PCRE2_MATCH_UNSET_BACKREF match_word set PCRE2_EXTRA_MATCH_WORD /m multiline set PCRE2_MULTILINE never_backslash_c set PCRE2_NEVER_BACKSLASH_C never_ucp set PCRE2_NEVER_UCP never_utf set PCRE2_NEVER_UTF /n no_auto_capture set PCRE2_NO_AUTO_CAPTURE no_auto_possess set PCRE2_NO_AUTO_POSSESS no_dotstar_anchor set PCRE2_NO_DOTSTAR_ANCHOR no_start_optimize set PCRE2_NO_START_OPTIMIZE no_utf_check set PCRE2_NO_UTF_CHECK ucp set PCRE2_UCP ungreedy set PCRE2_UNGREEDY use_offset_limit set PCRE2_USE_OFFSET_LIMIT utf set PCRE2_UTF As well as turning on the PCRE2_UTF option, the utf modifier causes all non-printing characters in output strings to be printed using the \ex{hh...} notation. Otherwise, those less than 0x100 are output in hex without the curly brackets. Setting utf in 16-bit or 32-bit mode also causes pattern and subject strings to be translated to UTF-16 or UTF-32, respectively, before being passed to library functions. . . HTML <a name="controlmodifiers"></a>
The newline modifier specifies which characters are to be interpreted as newlines, both in the pattern and in subject lines. The type must be one of CR, LF, CRLF, ANYCRLF, ANY, or NUL (in upper or lower case). . .
The bincode modifier causes a representation of the compiled code to be output after compilation. This information does not contain length and offset values, which ensures that the same output is generated for different internal link sizes and different code unit widths. By using bincode, the same regression tests can be used in different environments.
The fullbincode modifier, by contrast, does include length and offset values. This is used in a few special tests that run only for specific code unit widths and link sizes, and is also useful for one-off tests.
The info modifier requests information about the compiled pattern (whether it is anchored, has a fixed first character, and so on). The information is obtained from the pcre2_pattern_info() function. Here are some typical examples: re> /(?i)(^a|^b)/m,info Capturing subpattern count = 1 Compile options: multiline Overall options: caseless multiline First code unit at start or follows newline Subject length lower bound = 1 re> /(?i)abc/info Capturing subpattern count = 0 Compile options: <none> Overall options: caseless First code unit = 'a' (caseless) Last code unit = 'c' (caseless) Subject length lower bound = 3 "Compile options" are those specified by modifiers; "overall options" have added options that are taken or deduced from the pattern. If both sets of options are the same, just a single "options" line is output; if there are no options, the line is omitted. "First code unit" is where any match must start; if there is more than one they are listed as "starting code units". "Last code unit" is the last literal code unit that must be present in any match. This is not necessarily the last character. These lines are omitted if no starting or ending code units are recorded.
The framesize modifier shows the size, in bytes, of the storage frames used by pcre2_match() for handling backtracking. The size depends on the number of capturing parentheses in the pattern.
The callout_info modifier requests information about all the callouts in the pattern. A list of them is output at the end of any other information that is requested. For each callout, either its number or string is given, followed by the item that follows it in the pattern. . .
If hex or use_length is used with the POSIX wrapper API (see
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"Using the POSIX wrapper API"
below), the REG_PEND extension is used to pass the pattern's length.
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</a>
"Input encoding"
above. . .
If part of an expanded pattern looks like an expansion, but is really part of the actual pattern, unwanted expansion can be avoided by giving two values in the quantifier. For example, \e[AB]{6000,6000} is not recognized as an expansion item.
If the info modifier is set on an expanded pattern, the result of the expansion is included in the information that is output. . .
pcre2jit
documentation for details. JIT compiling happens, optionally, after a pattern has been successfully compiled into an internal form. The JIT compiler converts this to optimized machine code. It needs to know whether the match-time options PCRE2_PARTIAL_HARD and PCRE2_PARTIAL_SOFT are going to be used, because different code is generated for the different cases. See the partial modifier in "Subject Modifiers" HTML <a href="#subjectmodifiers">
</a>
below
for details of how these options are specified for each match attempt.
JIT compilation is requested by the jit pattern modifier, which may optionally be followed by an equals sign and a number in the range 0 to 7. The three bits that make up the number specify which of the three JIT operating modes are to be compiled: 1 compile JIT code for non-partial matching 2 compile JIT code for soft partial matching 4 compile JIT code for hard partial matching The possible values for the jit modifier are therefore: 0 disable JIT 1 normal matching only 2 soft partial matching only 3 normal and soft partial matching 4 hard partial matching only 6 soft and hard partial matching only 7 all three modes If no number is given, 7 is assumed. The phrase "partial matching" means a call to pcre2_match() with either the PCRE2_PARTIAL_SOFT or the PCRE2_PARTIAL_HARD option set. Note that such a call may return a complete match; the options enable the possibility of a partial match, but do not require it. Note also that if you request JIT compilation only for partial matching (for example, jit=2) but do not set the partial modifier on a subject line, that match will not use JIT code because none was compiled for non-partial matching.
If JIT compilation is successful, the compiled JIT code will automatically be
used when an appropriate type of match is run, except when incompatible
run-time options are specified. For more details, see the
HREF
pcre2jit
documentation. See also the jitstack modifier below for a way of
setting the size of the JIT stack.
If the jitfast modifier is specified, matching is done using the JIT "fast path" interface, pcre2_jit_match(), which skips some of the sanity checks that are done by pcre2_match(), and of course does not work when JIT is not supported. If jitfast is specified without jit, jit=7 is assumed.
If the jitverify modifier is specified, information about the compiled pattern shows whether JIT compilation was or was not successful. If jitverify is specified without jit, jit=7 is assumed. If JIT compilation is successful when jitverify is set, the text "(JIT)" is added to the first output line after a match or non match when JIT-compiled code was actually used in the match. . .
pcre2posix
documentation. The following pattern modifiers set options for the regcomp() function: caseless REG_ICASE multiline REG_NEWLINE dotall REG_DOTALL ) ungreedy REG_UNGREEDY ) These options are not part of ucp REG_UCP ) the POSIX standard utf REG_UTF8 ) The regerror_buffsize modifier specifies a size for the error buffer that is passed to regerror() in the event of a compilation error. For example: /abc/posix,regerror_buffsize=20 This provides a means of testing the behaviour of regerror() when the buffer is too small for the error message. If this modifier has not been set, a large buffer is used.
The aftertext and allaftertext subject modifiers work as described below. All other modifiers are either ignored, with a warning message, or cause an error.
The pattern is passed to regcomp() as a zero-terminated string by default, but if the use_length or hex modifiers are set, the REG_PEND extension is used to pass it by length. . .
pcre2api
documentation for details). If the number specified by the modifier is greater than zero, pcre2_set_compile_recursion_guard() is called to set up callback from pcre2_compile() to a local function. The argument it receives is the current nesting parenthesis depth; if this is greater than the value given by the modifier, non-zero is returned, causing the compilation to be aborted. . .
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below.
If pushcopy is used instead of push, a copy of the compiled pattern is stacked, leaving the original as current, ready to match the following input lines. This provides a way of testing the pcre2_code_copy() function.
The push and pushcopy modifiers are incompatible with compilation modifiers such as global that act at match time. Any that are specified are ignored (for the stacked copy), with a warning message, except for replace, which causes an error. Note that jitverify, which is allowed, does not carry through to any subsequent matching that uses a stacked pattern. . .
By default, the conversion function is allowed to allocate a buffer for its output. However, if the convert_length modifier is set to a value greater than zero, pcre2test passes a buffer of the given length. This makes it possible to test the length check.
The convert_glob_escape and convert_glob_separator modifiers can be
used to specify the escape and separator characters for glob processing,
overriding the defaults, which are operating-system dependent.
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.
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pcreapi
for a description of their effects. anchored set PCRE2_ANCHORED endanchored set PCRE2_ENDANCHORED dfa_restart set PCRE2_DFA_RESTART dfa_shortest set PCRE2_DFA_SHORTEST no_jit set PCRE2_NO_JIT no_utf_check set PCRE2_NO_UTF_CHECK notbol set PCRE2_NOTBOL notempty set PCRE2_NOTEMPTY notempty_atstart set PCRE2_NOTEMPTY_ATSTART noteol set PCRE2_NOTEOL partial_hard (or ph) set PCRE2_PARTIAL_HARD partial_soft (or ps) set PCRE2_PARTIAL_SOFT The partial matching modifiers are provided with abbreviations because they appear frequently in tests.
If the posix or posix_nosub modifier was present on the pattern, causing the POSIX wrapper API to be used, the only option-setting modifiers that have any effect are notbol, notempty, and noteol, causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively, to be passed to regexec(). The other modifiers are ignored, with a warning message.
There is one additional modifier that can be used with the POSIX wrapper. It is
ignored (with a warning) if used for non-POSIX matching.
posix_startend=<n>[:<m>]
This causes the subject string to be passed to regexec() using the
REG_STARTEND option, which uses offsets to specify which part of the string is
searched. If only one number is given, the end offset is passed as the end of
the subject string. For more detail of REG_STARTEND, see the
HREF
pcre2posix
documentation. If the subject string contains binary zeros (coded as escapes
such as \ex{00} because pcre2test does not support actual binary zeros in
its input), you must use posix_startend to specify its length.
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The allusedtext modifier requests that all the text that was consulted during a successful pattern match by the interpreter should be shown. This feature is not supported for JIT matching, and if requested with JIT it is ignored (with a warning message). Setting this modifier affects the output if there is a lookbehind at the start of a match, or a lookahead at the end, or if \eK is used in the pattern. Characters that precede or follow the start and end of the actual match are indicated in the output by '<' or '>' characters underneath them. Here is an example: re> /(?<=pqr)abc(?=xyz)/ data> 123pqrabcxyz456\e=allusedtext 0: pqrabcxyz <<< >>> This shows that the matched string is "abc", with the preceding and following strings "pqr" and "xyz" having been consulted during the match (when processing the assertions).
The startchar modifier requests that the starting character for the match be indicated, if it is different to the start of the matched string. The only time when this occurs is when \eK has been processed as part of the match. In this situation, the output for the matched string is displayed from the starting character instead of from the match point, with circumflex characters under the earlier characters. For example: re> /abc\eKxyz/ data> abcxyz\e=startchar 0: abcxyz ^^^ Unlike allusedtext, the startchar modifier can be used with JIT. However, these two modifiers are mutually exclusive. . .
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below.
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If an empty string is matched, the next match is done with the PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED flags set, in order to search for another, non-empty, match at the same point in the subject. If this match fails, the start offset is advanced, and the normal match is retried. This imitates the way Perl handles such cases when using the /g modifier or the split() function. Normally, the start offset is advanced by one character, but if the newline convention recognizes CRLF as a newline, and the current character is CR followed by LF, an advance of two characters occurs. . .
The getall modifier tests pcre2_substring_list_get(), which extracts all captured substrings.
If the subject line 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 substring, followed by the name when the extraction was by name. . .
Unlike subject strings, pcre2test does not process replacement strings for escape sequences. In UTF mode, a replacement string is checked to see if it is a valid UTF-8 string. If so, it is correctly converted to a UTF string of the appropriate code unit width. If it is not a valid UTF-8 string, the individual code units are copied directly. This provides a means of passing an invalid UTF-8 string for testing purposes.
The following modifiers set options (in additional to the normal match options) for pcre2_substitute(): global PCRE2_SUBSTITUTE_GLOBAL substitute_extended PCRE2_SUBSTITUTE_EXTENDED substitute_overflow_length PCRE2_SUBSTITUTE_OVERFLOW_LENGTH substitute_unknown_unset PCRE2_SUBSTITUTE_UNKNOWN_UNSET substitute_unset_empty PCRE2_SUBSTITUTE_UNSET_EMPTY
After a successful substitution, the modified string is output, preceded by the number of replacements. This may be zero if there were no matches. Here is a simple example of a substitution test: /abc/replace=xxx =abc=abc= 1: =xxx=abc= =abc=abc=\e=global 2: =xxx=xxx= Subject and replacement strings should be kept relatively short (fewer than 256 characters) for substitution tests, as fixed-size buffers are used. To make it easy to test for buffer overflow, if the replacement string starts with a number in square brackets, that number is passed to pcre2_substitute() as the size of the output buffer, with the replacement string starting at the next character. Here is an example that tests the edge case: /abc/ 123abc123\e=replace=[10]XYZ 1: 123XYZ123 123abc123\e=replace=[9]XYZ Failed: error -47: no more memory The default action of pcre2_substitute() is to return PCRE2_ERROR_NOMEMORY when the output buffer is too small. However, if the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set (by using the substitute_overflow_length modifier), pcre2_substitute() continues to go through the motions of matching and substituting, in order to compute the size of buffer that is required. When this happens, pcre2test shows the required buffer length (which includes space for the trailing zero) as part of the error message. For example: /abc/substitute_overflow_length 123abc123\e=replace=[9]XYZ Failed: error -47: no more memory: 10 code units are needed A replacement string is ignored with POSIX and DFA matching. Specifying partial matching provokes an error return ("bad option value") from pcre2_substitute(). . .
When using this modifier, the pattern should not contain any limit settings such as (*LIMIT_MATCH=...) within it. If such a setting is present and is lower than the minimum matching value, the minimum value cannot be found because pcre2_set_match_limit() etc. are only able to reduce the value of an in-pattern limit; they cannot increase it.
For non-DFA matching, the minimum depth_limit number is a measure of how much nested backtracking happens (that is, how deeply the pattern's tree is searched). In the case of DFA matching, depth_limit controls the depth of recursive calls of the internal function that is used for handling pattern recursion, lookaround assertions, and atomic groups.
For non-DFA matching, the match_limit number is a measure of the amount of backtracking that takes place, and learning the minimum value 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. In the case of DFA matching, match_limit controls the total number of calls, both recursive and non-recursive, to the internal matching function, thus controlling the overall amount of computing resource that is used.
For both kinds of matching, the heap_limit number, which is in kibibytes (units of 1024 bytes), limits the amount of heap memory used for matching. A value of zero disables the use of any heap memory; many simple pattern matches can be done without using the heap, so zero is not an unreasonable setting. . .
The mark modifier causes the names from backtracking control verbs that are returned from calls to pcre2_match() to be displayed. If a mark is returned for a match, non-match, or partial match, pcre2test shows it. For a match, it is on a line by itself, tagged with "MK:". Otherwise, it is added to the non-match message. . .
A value of zero is useful when testing the POSIX API because it causes regexec() to be called with a NULL capture vector. When not testing the POSIX API, a value of zero is used to cause pcre2_match_data_create_from_pattern() to be called, in order to create a match block of exactly the right size for the pattern. (It is not possible to create a match block with a zero-length ovector; there is always at least one pair of offsets.) . .
When testing pcre2_substitute(), this modifier also has the effect of passing the replacement string as zero-terminated. . .
pcre2matching
documentation.
If the dfa modifier is set, the alternative matching function is used. This function finds all possible matches at a given point in the subject. If, however, the dfa_shortest modifier is set, processing stops after the first match is found. This is always the shortest possible match. . .
When a match succeeds, pcre2test outputs the list of captured substrings, starting with number 0 for the string that matched the whole pattern. Otherwise, it outputs "No match" when the return is PCRE2_ERROR_NOMATCH, or "Partial match:" followed by the partially matching substring when the return is PCRE2_ERROR_PARTIAL. (Note that this is the entire substring that was inspected during the partial match; it may include characters before the actual match start if a lookbehind assertion, \eK, \eb, or \eB was involved.)
For any other return, pcre2test outputs the PCRE2 negative error number and a short descriptive phrase. If the error is a failed UTF string check, the code unit offset of the start of the failing character is also output. Here is an example of an interactive pcre2test run. $ pcre2test PCRE2 version 10.22 2016-07-29 re> /^abc(\ed+)/ data> abc123 0: abc123 1: 123 data> xyz No match Unset capturing substrings that are not followed by one that is set are not shown by pcre2test unless the allcaptures modifier is specified. 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 \exhh escapes if the value is less than 256 and UTF mode is not set. Otherwise they are output as \ex{hh...} escapes. See below for the definition of non-printing characters. If the aftertext modifier is set, the output for substring 0 is followed by the the rest of the subject string, identified by "0+" like this: re> /cat/aftertext data> cataract 0: cat 0+ aract If global matching is requested, the results of successive matching attempts are output in sequence, like this: re> /\eBi(\ew\ew)/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. Here is an example of a failure message (the offset 4 that is specified by the offset modifier is past the end of the subject string): re> /xyz/ data> xyz\e=offset=4 Error -24 (bad offset value)
Note that whereas patterns can be continued over several lines (a plain ">" prompt is used for continuations), subject lines may not. However newlines can be included in a subject by means of the \en escape (or \er, \er\en, etc., depending on the newline sequence setting). . . .
If global matching is requested, 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\e=dfa 0: tangerine 1: tang 2: tan 0: tang 1: tan 0: tan The alternative matching function does not support substring capture, so the modifiers that are concerned with captured substrings are not relevant. . .
pcre2partial
documentation. . . HTML <a name="callouts"></a>
Callouts numbered 255 are assumed to be automatic callouts, inserted as a result of the auto_callout 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> /\ed?[A-E]\e*/auto_callout data> E* --->E* +0 ^ \ed? +3 ^ [A-E] +8 ^^ \e* +10 ^ ^ 0: E* If a pattern contains (*MARK) items, an additional line is output whenever a change of latest mark is passed to the callout function. For example: re> /a(*MARK:X)bc/auto_callout data> abc --->abc +0 ^ a +1 ^^ (*MARK:X) +10 ^^ b Latest Mark: X +11 ^ ^ c +12 ^ ^ 0: abc The mark changes between matching "a" and "b", but stays the same for the rest of the match, so nothing more is output. If, as a result of backtracking, the mark reverts to being unset, the text "<unset>" is output. . .
If the callout_capture modifier is set, the current captured groups are output when a callout occurs. This is useful only for non-DFA matching, as pcre2_dfa_match() does not support capturing, so no captures are ever shown.
The normal callout output, showing the callout number or pattern offset (as described above) is suppressed if the callout_no_where modifier is set.
When using the interpretive matching function pcre2_match() without JIT, setting the callout_extra modifier causes additional output from pcre2test's callout function to be generated. For the first callout in a match attempt at a new starting position in the subject, "New match attempt" is output. If there has been a backtrack since the last callout (or start of matching if this is the first callout), "Backtrack" is output, followed by "No other matching paths" if the backtrack ended the previous match attempt. For example: re> /(a+)b/auto_callout,no_start_optimize,no_auto_possess data> aac\e=callout_extra New match attempt --->aac +0 ^ ( +1 ^ a+ +3 ^ ^ ) +4 ^ ^ b Backtrack --->aac +3 ^^ ) +4 ^^ b Backtrack No other matching paths New match attempt --->aac +0 ^ ( +1 ^ a+ +3 ^^ ) +4 ^^ b Backtrack No other matching paths New match attempt --->aac +0 ^ ( +1 ^ a+ Backtrack No other matching paths New match attempt --->aac +0 ^ ( +1 ^ a+ No match Notice that various optimizations must be turned off if you want all possible matching paths to be scanned. If no_start_optimize is not used, there is an immediate "no match", without any callouts, because the starting optimization fails to find "b" in the subject, which it knows must be present for any match. If no_auto_possess is not used, the "a+" item is turned into "a++", which reduces the number of backtracks.
The callout_extra modifier has no effect if used with the DFA matching function, or with JIT. . .
The callout_data modifier can be given an unsigned or a negative number. This is set as the "user data" that is passed to the matching function, and passed back when the callout function is invoked. Any value other than zero is used as a return from pcre2test's callout function.
Inserting callouts can be helpful when using pcre2test to check
complicated regular expressions. For further information about callouts, see
the
HREF
pcre2callout
documentation.
.
.
.
When pcre2test is outputting text that is a matched part of a subject
string, it behaves in the same way, unless a different locale has been set for
the pattern (using the locale modifier). In this case, the
isprint() function is used to distinguish printing and non-printing
characters.
.
.
.
HTML <a name="saverestore"></a>
The functions whose names begin with pcre2_serialize_ are used
for serializing and de-serializing. They are described in the
HREF
pcre2serialize
documentation. In this section we describe the features of pcre2test that
can be used to test these functions.
Note that "serialization" in PCRE2 does not convert compiled patterns to an abstract format like Java or .NET. It just makes a reloadable byte code stream. Hence the restrictions on reloading mentioned above.
In pcre2test, when a pattern with push modifier is successfully compiled, it is pushed onto a stack of compiled patterns, and pcre2test expects the next line to contain a new pattern (or command) instead of a subject line. By contrast, the pushcopy modifier causes a copy of the compiled pattern to be stacked, leaving the original available for immediate matching. By using push and/or pushcopy, a number of patterns can be compiled and retained. These modifiers are incompatible with posix, and control modifiers that act at match time are ignored (with a message) for the stacked patterns. The jitverify modifier applies only at compile time.
The command
#save <filename>
causes all the stacked patterns to be serialized and the result written to the
named file. Afterwards, all the stacked patterns are freed. The command
#load <filename>
reads the data in the file, and then arranges for it to be de-serialized, with
the resulting compiled patterns added to the pattern stack. The pattern on the
top of the stack can be retrieved by the #pop command, which must be followed
by lines of subjects that are to be matched with the pattern, terminated as
usual by an empty line or end of file. This command may be followed by a
modifier list containing only
HTML <a href="#controlmodifiers">
</a>
control modifiers
that act after a pattern has been compiled. In particular, hex,
posix, posix_nosub, push, and pushcopy are not allowed,
nor are any
HTML <a href="#optionmodifiers">
</a>
option-setting modifiers.
The JIT modifiers are, however permitted. Here is an example that saves and
reloads two patterns.
/abc/push
/xyz/push
#save tempfile
#load tempfile
#pop info
xyz
#pop jit,bincode
abc
If jitverify is used with #pop, it does not automatically imply
jit, which is different behaviour from when it is used on a pattern.
The #popcopy command is analagous to the pushcopy modifier in that it makes current a copy of the topmost stack pattern, leaving the original still on the stack. . . .
Philip Hazel University Computing Service Cambridge, England.. .
Last updated: 21 July 2018 Copyright (c) 1997-2018 University of Cambridge.