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Documentation update.

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Philip.Hazel 2020-02-16 17:47:14 +00:00
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doc/html/pcre2api.html
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@ -3309,13 +3309,13 @@ can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. There is an
option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to return just the
replacement string(s). The default action is to perform just one replacement if
the pattern matches, but there is an option that requests multiple replacements
(see PCRE2_SUBSTITUTE_GLOBAL below for details).
(see PCRE2_SUBSTITUTE_GLOBAL below).
</P>
<P>
If successful, <b>pcre2_substitute()</b> returns the number of substitutions
that were carried out. This may be zero if no match was found, and is never
greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A negative value is
returned if an error is detected (see below for details).
returned if an error is detected.
</P>
<P>
Matches in which a \K item in a lookahead in the pattern causes the match to
@ -3333,10 +3333,11 @@ functions from the match context, if provided, or else those that were used to
allocate memory for the compiled code.
</P>
<P>
If an external <i>match_data</i> block is provided, its contents afterwards
are those set by the final call to <b>pcre2_match()</b>. For global changes,
this will have ended in a no-match error. The contents of the ovector within
the match data block may or may not have been changed.
If <i>match_data</i> is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the
provided block is used for all calls to <b>pcre2_match()</b>, and its contents
afterwards are the result of the final call. For global changes, this will
always be a no-match error. The contents of the ovector within the match data
block may or may not have been changed.
</P>
<P>
As well as the usual options for <b>pcre2_match()</b>, a number of additional
@ -3350,45 +3351,68 @@ an application to check for a match before choosing to substitute, without
having to repeat the match.
</P>
<P>
The <i>code</i> argument is not used for the first substitution when
PCRE2_SUBSTITUTE_MATCHED is set, but if PCRE2_SUBSTITUTE_GLOBAL is also set,
<b>pcre2_match()</b> will be called after the first substitution to check for
further matches, and the contents of the <i>match_data</i> block will be
changed.
The contents of the externally supplied match data block are not changed when
PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTITUTE_GLOBAL is also set,
<b>pcre2_match()</b> is called after the first substitution to check for further
matches, but this is done using an internally obtained match data block, thus
always leaving the external block unchanged.
</P>
<P>
The default is to return a copy of the subject string with matched substrings
replaced. However, if PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set, only the
replacement substrings are returned. In the global case, multiple replacements
are concatenated in the output buffer. Substitution callouts (see
The <i>code</i> argument is not used for matching before the first substitution
when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided, even when
PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains information such as the
UTF setting and the number of capturing parentheses in the pattern.
</P>
<P>
The default action of <b>pcre2_substitute()</b> is to return a copy of the
subject string with matched substrings replaced. However, if
PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are
returned. In the global case, multiple replacements are concatenated in the
output buffer. Substitution callouts (see
<a href="#subcallouts">below)</a>
can be used to separate them if necessary.
</P>
<P>
The <i>outlengthptr</i> argument of <b>pcre2_substitute()</b> must point to a
variable that contains the length, in code units, of the output buffer. If the
function is successful, the value is updated to contain the length of the new
string, excluding the trailing zero that is automatically added.
function is successful, the value is updated to contain the length in code
units of the new string, excluding the trailing zero that is automatically
added.
</P>
<P>
If the function is not successful, the value set via <i>outlengthptr</i> depends
on the type of error. For syntax errors in the replacement string, the value is
the offset in the replacement string where the error was detected. For other
errors, the value is PCRE2_UNSET by default. This includes the case of the
output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set
(see below), in which case the value is the minimum length needed, including
space for the trailing zero. Note that in order to compute the required length,
<b>pcre2_substitute()</b> has to simulate all the matching and copying, instead
of giving an error return as soon as the buffer overflows. Note also that the
length is in code units, not bytes.
output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set.
</P>
<P>
The replacement string, which is interpreted as a UTF string in UTF mode,
is checked for UTF validity unless the PCRE2_NO_UTF_CHECK option is set. If the
PCRE2_SUBSTITUTE_LITERAL option is set, it is not interpreted in any way. By
default, however, a dollar character is an escape character that can specify
the insertion of characters from capture groups and names from (*MARK) or other
control verbs in the pattern. The following forms are always recognized:
PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is
too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If
this option is set, however, <b>pcre2_substitute()</b> continues to go through
the motions of matching and substituting (without, of course, writing anything)
in order to compute the size of buffer that is needed. This value is passed
back via the <i>outlengthptr</i> variable, with the result of the function still
being PCRE2_ERROR_NOMEMORY.
</P>
<P>
Passing a buffer size of zero is a permitted way of finding out how much memory
is needed for given substitution. However, this does mean that the entire
operation is carried out twice. Depending on the application, it may be more
efficient to allocate a large buffer and free the excess afterwards, instead of
using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH.
</P>
<P>
The replacement string, which is interpreted as a UTF string in UTF mode, is
checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An invalid UTF
replacement string causes an immediate return with the relevant UTF error code.
</P>
<P>
If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not interpreted
in any way. By default, however, a dollar character is an escape character that
can specify the insertion of characters from capture groups and names from
(*MARK) or other control verbs in the pattern. The following forms are always
recognized:
<pre>
$$ insert a dollar character
$&#60;n&#62; or ${&#60;n&#62;} insert the contents of group &#60;n&#62;
@ -3436,22 +3460,6 @@ CRLF is a valid newline sequence and the next two characters are CR, LF. In
this case, the offset is advanced by two characters.
</P>
<P>
PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is
too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If
this option is set, however, <b>pcre2_substitute()</b> continues to go through
the motions of matching and substituting (without, of course, writing anything)
in order to compute the size of buffer that is needed. This value is passed
back via the <i>outlengthptr</i> variable, with the result of the function still
being PCRE2_ERROR_NOMEMORY.
</P>
<P>
Passing a buffer size of zero is a permitted way of finding out how much memory
is needed for given substitution. However, this does mean that the entire
operation is carried out twice. Depending on the application, it may be more
efficient to allocate a large buffer and free the excess afterwards, instead of
using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH.
</P>
<P>
PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that do
not appear in the pattern to be treated as unset groups. This option should be
used with care, because it means that a typo in a group name or number no
@ -3907,7 +3915,7 @@ Cambridge, England.
</P>
<br><a name="SEC42" href="#TOC1">REVISION</a><br>
<P>
Last updated: 22 January 2020
Last updated: 16 February 2020
<br>
Copyright &copy; 1997-2020 University of Cambridge.
<br>

485
doc/pcre2.txt
View File

@ -3200,13 +3200,13 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
There is an option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to re-
turn just the replacement string(s). The default action is to perform
just one replacement if the pattern matches, but there is an option
that requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below
for details).
that requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL be-
low).
If successful, pcre2_substitute() returns the number of substitutions
that were carried out. This may be zero if no match was found, and is
never greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A nega-
tive value is returned if an error is detected (see below for details).
tive value is returned if an error is detected.
Matches in which a \K item in a lookahead in the pattern causes the
match to end before it starts are not supported, and give rise to an
@ -3221,104 +3221,54 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
ment functions from the match context, if provided, or else those that
were used to allocate memory for the compiled code.
If an external match_data block is provided, its contents afterwards
are those set by the final call to pcre2_match(). For global changes,
this will have ended in a no-match error. The contents of the ovector
within the match data block may or may not have been changed.
If match_data is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the
provided block is used for all calls to pcre2_match(), and its contents
afterwards are the result of the final call. For global changes, this
will always be a no-match error. The contents of the ovector within the
match data block may or may not have been changed.
As well as the usual options for pcre2_match(), a number of additional
options can be set in the options argument of pcre2_substitute(). One
such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external
match_data block must be provided, and it must have been used for an
external call to pcre2_match(). The data in the match_data block (re-
As well as the usual options for pcre2_match(), a number of additional
options can be set in the options argument of pcre2_substitute(). One
such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external
match_data block must be provided, and it must have been used for an
external call to pcre2_match(). The data in the match_data block (re-
turn code, offset vector) is used for the first substitution instead of
calling pcre2_match() from within pcre2_substitute(). This allows an
calling pcre2_match() from within pcre2_substitute(). This allows an
application to check for a match before choosing to substitute, without
having to repeat the match.
The code argument is not used for the first substitution when
PCRE2_SUBSTITUTE_MATCHED is set, but if PCRE2_SUBSTITUTE_GLOBAL is also
set, pcre2_match() will be called after the first substitution to check
for further matches, and the contents of the match_data block will be
changed.
The contents of the externally supplied match data block are not
changed when PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTI-
TUTE_GLOBAL is also set, pcre2_match() is called after the first sub-
stitution to check for further matches, but this is done using an in-
ternally obtained match data block, thus always leaving the external
block unchanged.
The default is to return a copy of the subject string with matched sub-
strings replaced. However, if PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set,
only the replacement substrings are returned. In the global case, mul-
tiple replacements are concatenated in the output buffer. Substitution
callouts (see below) can be used to separate them if necessary.
The code argument is not used for matching before the first substitu-
tion when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided,
even when PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains in-
formation such as the UTF setting and the number of capturing parenthe-
ses in the pattern.
The outlengthptr argument of pcre2_substitute() must point to a vari-
able that contains the length, in code units, of the output buffer. If
the function is successful, the value is updated to contain the length
of the new string, excluding the trailing zero that is automatically
added.
The default action of pcre2_substitute() is to return a copy of the
subject string with matched substrings replaced. However, if PCRE2_SUB-
STITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are
returned. In the global case, multiple replacements are concatenated in
the output buffer. Substitution callouts (see below) can be used to
separate them if necessary.
If the function is not successful, the value set via outlengthptr de-
pends on the type of error. For syntax errors in the replacement
The outlengthptr argument of pcre2_substitute() must point to a vari-
able that contains the length, in code units, of the output buffer. If
the function is successful, the value is updated to contain the length
in code units of the new string, excluding the trailing zero that is
automatically added.
If the function is not successful, the value set via outlengthptr de-
pends on the type of error. For syntax errors in the replacement
string, the value is the offset in the replacement string where the er-
ror was detected. For other errors, the value is PCRE2_UNSET by de-
ror was detected. For other errors, the value is PCRE2_UNSET by de-
fault. This includes the case of the output buffer being too small, un-
less PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set (see below), in which case
the value is the minimum length needed, including space for the trail-
ing zero. Note that in order to compute the required length, pcre2_sub-
stitute() has to simulate all the matching and copying, instead of giv-
ing an error return as soon as the buffer overflows. Note also that the
length is in code units, not bytes.
The replacement string, which is interpreted as a UTF string in UTF
mode, is checked for UTF validity unless the PCRE2_NO_UTF_CHECK option
is set. If the PCRE2_SUBSTITUTE_LITERAL option is set, it is not inter-
preted in any way. By default, however, a dollar character is an escape
character that can specify the insertion of characters from capture
groups and names from (*MARK) or other control verbs in the pattern.
The following forms are always recognized:
$$ insert a dollar character
$<n> or ${<n>} insert the contents of group <n>
$*MARK or ${*MARK} insert a control verb name
Either a group number or a group name can be given for <n>. Curly
brackets are required only if the following character would be inter-
preted as part of the number or name. The number may be zero to include
the entire matched string. For example, if the pattern a(b)c is
matched with "=abc=" and the replacement string "+$1$0$1+", the result
is "=+babcb+=".
$*MARK inserts the name from the last encountered backtracking control
verb on the matching path that has a name. (*MARK) must always include
a name, but the other verbs need not. For example, in the case of
(*MARK:A)(*PRUNE) the name inserted is "A", but for (*MARK:A)(*PRUNE:B)
the relevant name is "B". This facility can be used to perform simple
simultaneous substitutions, as this pcre2test example shows:
/(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK}
apple lemon
2: pear orange
PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject
string, replacing every matching substring. If this option is not set,
only the first matching substring is replaced. The search for matches
takes place in the original subject string (that is, previous replace-
ments do not affect it). Iteration is implemented by advancing the
startoffset value for each search, which is always passed the entire
subject string. If an offset limit is set in the match context, search-
ing stops when that limit is reached.
You can restrict the effect of a global substitution to a portion of
the subject string by setting either or both of startoffset and an off-
set limit. Here is a pcre2test example:
/B/g,replace=!,use_offset_limit
ABC ABC ABC ABC\=offset=3,offset_limit=12
2: ABC A!C A!C ABC
When continuing with global substitutions after matching a substring
with zero length, an attempt to find a non-empty match at the same off-
set is performed. If this is not successful, the offset is advanced by
one character except when CRLF is a valid newline sequence and the next
two characters are CR, LF. In this case, the offset is advanced by two
characters.
less PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set.
PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output
buffer is too small. The default action is to return PCRE2_ERROR_NOMEM-
@ -3336,64 +3286,121 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
the excess afterwards, instead of using PCRE2_SUBSTITUTE_OVER-
FLOW_LENGTH.
The replacement string, which is interpreted as a UTF string in UTF
mode, is checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An
invalid UTF replacement string causes an immediate return with the rel-
evant UTF error code.
If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not in-
terpreted in any way. By default, however, a dollar character is an es-
cape character that can specify the insertion of characters from cap-
ture groups and names from (*MARK) or other control verbs in the pat-
tern. The following forms are always recognized:
$$ insert a dollar character
$<n> or ${<n>} insert the contents of group <n>
$*MARK or ${*MARK} insert a control verb name
Either a group number or a group name can be given for <n>. Curly
brackets are required only if the following character would be inter-
preted as part of the number or name. The number may be zero to include
the entire matched string. For example, if the pattern a(b)c is
matched with "=abc=" and the replacement string "+$1$0$1+", the result
is "=+babcb+=".
$*MARK inserts the name from the last encountered backtracking control
verb on the matching path that has a name. (*MARK) must always include
a name, but the other verbs need not. For example, in the case of
(*MARK:A)(*PRUNE) the name inserted is "A", but for (*MARK:A)(*PRUNE:B)
the relevant name is "B". This facility can be used to perform simple
simultaneous substitutions, as this pcre2test example shows:
/(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK}
apple lemon
2: pear orange
PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject
string, replacing every matching substring. If this option is not set,
only the first matching substring is replaced. The search for matches
takes place in the original subject string (that is, previous replace-
ments do not affect it). Iteration is implemented by advancing the
startoffset value for each search, which is always passed the entire
subject string. If an offset limit is set in the match context, search-
ing stops when that limit is reached.
You can restrict the effect of a global substitution to a portion of
the subject string by setting either or both of startoffset and an off-
set limit. Here is a pcre2test example:
/B/g,replace=!,use_offset_limit
ABC ABC ABC ABC\=offset=3,offset_limit=12
2: ABC A!C A!C ABC
When continuing with global substitutions after matching a substring
with zero length, an attempt to find a non-empty match at the same off-
set is performed. If this is not successful, the offset is advanced by
one character except when CRLF is a valid newline sequence and the next
two characters are CR, LF. In this case, the offset is advanced by two
characters.
PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that
do not appear in the pattern to be treated as unset groups. This option
should be used with care, because it means that a typo in a group name
should be used with care, because it means that a typo in a group name
or number no longer causes the PCRE2_ERROR_NOSUBSTRING error.
PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including un-
known groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated
as empty strings when inserted as described above. If this option is
known groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated
as empty strings when inserted as described above. If this option is
not set, an attempt to insert an unset group causes the PCRE2_ERROR_UN-
SET error. This option does not influence the extended substitution
SET error. This option does not influence the extended substitution
syntax described below.
PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
replacement string. Without this option, only the dollar character is
special, and only the group insertion forms listed above are valid.
PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
replacement string. Without this option, only the dollar character is
special, and only the group insertion forms listed above are valid.
When PCRE2_SUBSTITUTE_EXTENDED is set, two things change:
Firstly, backslash in a replacement string is interpreted as an escape
Firstly, backslash in a replacement string is interpreted as an escape
character. The usual forms such as \n or \x{ddd} can be used to specify
particular character codes, and backslash followed by any non-alphanu-
meric character quotes that character. Extended quoting can be coded
particular character codes, and backslash followed by any non-alphanu-
meric character quotes that character. Extended quoting can be coded
using \Q...\E, exactly as in pattern strings.
There are also four escape sequences for forcing the case of inserted
letters. The insertion mechanism has three states: no case forcing,
There are also four escape sequences for forcing the case of inserted
letters. The insertion mechanism has three states: no case forcing,
force upper case, and force lower case. The escape sequences change the
current state: \U and \L change to upper or lower case forcing, respec-
tively, and \E (when not terminating a \Q quoted sequence) reverts to
no case forcing. The sequences \u and \l force the next character (if
it is a letter) to upper or lower case, respectively, and then the
tively, and \E (when not terminating a \Q quoted sequence) reverts to
no case forcing. The sequences \u and \l force the next character (if
it is a letter) to upper or lower case, respectively, and then the
state automatically reverts to no case forcing. Case forcing applies to
all inserted characters, including those from capture groups and let-
all inserted characters, including those from capture groups and let-
ters within \Q...\E quoted sequences.
Note that case forcing sequences such as \U...\E do not nest. For exam-
ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
\E has no effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EX-
ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
\E has no effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EX-
TRA_ALT_BSUX options do not apply to replacement strings.
The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
flexibility to capture group substitution. The syntax is similar to
The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
flexibility to capture group substitution. The syntax is similar to
that used by Bash:
${<n>:-<string>}
${<n>:+<string1>:<string2>}
As before, <n> may be a group number or a name. The first form speci-
fies a default value. If group <n> is set, its value is inserted; if
not, <string> is expanded and the result inserted. The second form
specifies strings that are expanded and inserted when group <n> is set
or unset, respectively. The first form is just a convenient shorthand
As before, <n> may be a group number or a name. The first form speci-
fies a default value. If group <n> is set, its value is inserted; if
not, <string> is expanded and the result inserted. The second form
specifies strings that are expanded and inserted when group <n> is set
or unset, respectively. The first form is just a convenient shorthand
for
${<n>:+${<n>}:<string>}
Backslash can be used to escape colons and closing curly brackets in
the replacement strings. A change of the case forcing state within a
replacement string remains in force afterwards, as shown in this
Backslash can be used to escape colons and closing curly brackets in
the replacement strings. A change of the case forcing state within a
replacement string remains in force afterwards, as shown in this
pcre2test example:
/(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo
@ -3402,8 +3409,8 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
somebody
1: HELLO
The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause un-
The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause un-
known groups in the extended syntax forms to be treated as unset.
If PCRE2_SUBSTITUTE_LITERAL is set, PCRE2_SUBSTITUTE_UNKNOWN_UNSET,
@ -3412,37 +3419,37 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
Substitution errors
In the event of an error, pcre2_substitute() returns a negative error
code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors
In the event of an error, pcre2_substitute() returns a negative error
code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors
from pcre2_match() are passed straight back.
PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring inser-
tion, unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set.
PCRE2_ERROR_UNSET is returned for an unset substring insertion (includ-
ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
when the simple (non-extended) syntax is used and PCRE2_SUBSTITUTE_UN-
ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
when the simple (non-extended) syntax is used and PCRE2_SUBSTITUTE_UN-
SET_EMPTY is not set.
PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big
PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big
enough. If the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size
of buffer that is needed is returned via outlengthptr. Note that this
of buffer that is needed is returned via outlengthptr. Note that this
does not happen by default.
PCRE2_ERROR_NULL is returned if PCRE2_SUBSTITUTE_MATCHED is set but the
match_data argument is NULL.
PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in
the replacement string, with more particular errors being PCRE2_ER-
PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in
the replacement string, with more particular errors being PCRE2_ER-
ROR_BADREPESCAPE (invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE
(closing curly bracket not found), PCRE2_ERROR_BADSUBSTITUTION (syntax
error in extended group substitution), and PCRE2_ERROR_BADSUBSPATTERN
(closing curly bracket not found), PCRE2_ERROR_BADSUBSTITUTION (syntax
error in extended group substitution), and PCRE2_ERROR_BADSUBSPATTERN
(the pattern match ended before it started or the match started earlier
than the current position in the subject, which can happen if \K is
than the current position in the subject, which can happen if \K is
used in an assertion).
As for all PCRE2 errors, a text message that describes the error can be
obtained by calling the pcre2_get_error_message() function (see "Ob-
obtained by calling the pcre2_get_error_message() function (see "Ob-
taining a textual error message" above).
Substitution callouts
@ -3451,15 +3458,15 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
int (*callout_function)(pcre2_substitute_callout_block *, void *),
void *callout_data);
The pcre2_set_substitution_callout() function can be used to specify a
callout function for pcre2_substitute(). This information is passed in
The pcre2_set_substitution_callout() function can be used to specify a
callout function for pcre2_substitute(). This information is passed in
a match context. The callout function is called after each substitution
has been processed, but it can cause the replacement not to happen. The
callout function is not called for simulated substitutions that happen
callout function is not called for simulated substitutions that happen
as a result of the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option.
The first argument of the callout function is a pointer to a substitute
callout block structure, which contains the following fields, not nec-
callout block structure, which contains the following fields, not nec-
essarily in this order:
uint32_t version;
@ -3470,34 +3477,34 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
uint32_t oveccount;
PCRE2_SIZE output_offsets[2];
The version field contains the version number of the block format. The
current version is 0. The version number will increase in future if
more fields are added, but the intention is never to remove any of the
The version field contains the version number of the block format. The
current version is 0. The version number will increase in future if
more fields are added, but the intention is never to remove any of the
existing fields.
The subscount field is the number of the current match. It is 1 for the
first callout, 2 for the second, and so on. The input and output point-
ers are copies of the values passed to pcre2_substitute().
The ovector field points to the ovector, which contains the result of
The ovector field points to the ovector, which contains the result of
the most recent match. The oveccount field contains the number of pairs
that are set in the ovector, and is always greater than zero.
The output_offsets vector contains the offsets of the replacement in
the output string. This has already been processed for dollar and (if
The output_offsets vector contains the offsets of the replacement in
the output string. This has already been processed for dollar and (if
requested) backslash substitutions as described above.
The second argument of the callout function is the value passed as
callout_data when the function was registered. The value returned by
The second argument of the callout function is the value passed as
callout_data when the function was registered. The value returned by
the callout function is interpreted as follows:
If the value is zero, the replacement is accepted, and, if PCRE2_SUB-
STITUTE_GLOBAL is set, processing continues with a search for the next
match. If the value is not zero, the current replacement is not ac-
cepted. If the value is greater than zero, processing continues when
PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero
or PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is
copied to the output and the call to pcre2_substitute() exits, return-
If the value is zero, the replacement is accepted, and, if PCRE2_SUB-
STITUTE_GLOBAL is set, processing continues with a search for the next
match. If the value is not zero, the current replacement is not ac-
cepted. If the value is greater than zero, processing continues when
PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero
or PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is
copied to the output and the call to pcre2_substitute() exits, return-
ing the number of matches so far.
@ -3506,56 +3513,56 @@ DUPLICATE CAPTURE GROUP NAMES
int pcre2_substring_nametable_scan(const pcre2_code *code,
PCRE2_SPTR name, PCRE2_SPTR *first, PCRE2_SPTR *last);
When a pattern is compiled with the PCRE2_DUPNAMES option, names for
capture groups are not required to be unique. Duplicate names are al-
ways allowed for groups with the same number, created by using the (?|
When a pattern is compiled with the PCRE2_DUPNAMES option, names for
capture groups are not required to be unique. Duplicate names are al-
ways allowed for groups with the same number, created by using the (?|
feature. Indeed, if such groups are named, they are required to use the
same names.
Normally, patterns that use duplicate names are such that in any one
match, only one of each set of identically-named groups participates.
Normally, patterns that use duplicate names are such that in any one
match, only one of each set of identically-named groups participates.
An example is shown in the pcre2pattern documentation.
When duplicates are present, pcre2_substring_copy_byname() and
pcre2_substring_get_byname() return the first substring corresponding
to the given name that is set. Only if none are set is PCRE2_ERROR_UN-
SET is returned. The pcre2_substring_number_from_name() function re-
turns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate
When duplicates are present, pcre2_substring_copy_byname() and
pcre2_substring_get_byname() return the first substring corresponding
to the given name that is set. Only if none are set is PCRE2_ERROR_UN-
SET is returned. The pcre2_substring_number_from_name() function re-
turns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate
names.
If you want to get full details of all captured substrings for a given
name, you must use the pcre2_substring_nametable_scan() function. The
first argument is the compiled pattern, and the second is the name. If
the third and fourth arguments are NULL, the function returns a group
If you want to get full details of all captured substrings for a given
name, you must use the pcre2_substring_nametable_scan() function. The
first argument is the compiled pattern, and the second is the name. If
the third and fourth arguments are NULL, the function returns a group
number for a unique name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise.
When the third and fourth arguments are not NULL, they must be pointers
to variables that are updated by the function. After it has run, they
to variables that are updated by the function. After it has run, they
point to the first and last entries in the name-to-number table for the
given name, and the function returns the length of each entry in code
units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
given name, and the function returns the length of each entry in code
units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
no entries for the given name.
The format of the name table is described above in the section entitled
Information about a pattern. Given all the relevant entries for the
name, you can extract each of their numbers, and hence the captured
Information about a pattern. Given all the relevant entries for the
name, you can extract each of their numbers, and hence the captured
data.
FINDING ALL POSSIBLE MATCHES AT ONE POSITION
The traditional matching function uses a similar algorithm to Perl,
which stops when it finds the first match at a given point in the sub-
The traditional matching function uses a similar algorithm to Perl,
which stops when it finds the first match at a given point in the sub-
ject. If you want to find all possible matches, or the longest possible
match at a given position, consider using the alternative matching
function (see below) instead. If you cannot use the alternative func-
match at a given position, consider using the alternative matching
function (see below) instead. If you cannot use the alternative func-
tion, you can kludge it up by making use of the callout facility, which
is described in the pcre2callout documentation.
What you have to do is to insert a callout right at the end of the pat-
tern. When your callout function is called, extract and save the cur-
rent matched substring. Then return 1, which forces pcre2_match() to
backtrack and try other alternatives. Ultimately, when it runs out of
tern. When your callout function is called, extract and save the cur-
rent matched substring. Then return 1, which forces pcre2_match() to
backtrack and try other alternatives. Ultimately, when it runs out of
matches, pcre2_match() will yield PCRE2_ERROR_NOMATCH.
@ -3567,26 +3574,26 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
pcre2_match_context *mcontext,
int *workspace, PCRE2_SIZE wscount);
The function pcre2_dfa_match() is called to match a subject string
against a compiled pattern, using a matching algorithm that scans the
The function pcre2_dfa_match() is called to match a subject string
against a compiled pattern, using a matching algorithm that scans the
subject string just once (not counting lookaround assertions), and does
not backtrack. This has different characteristics to the normal algo-
rithm, and is not compatible with Perl. Some of the features of PCRE2
patterns are not supported. Nevertheless, there are times when this
kind of matching can be useful. For a discussion of the two matching
not backtrack. This has different characteristics to the normal algo-
rithm, and is not compatible with Perl. Some of the features of PCRE2
patterns are not supported. Nevertheless, there are times when this
kind of matching can be useful. For a discussion of the two matching
algorithms, and a list of features that pcre2_dfa_match() does not sup-
port, see the pcre2matching documentation.
The arguments for the pcre2_dfa_match() function are the same as for
The arguments for the pcre2_dfa_match() function are the same as for
pcre2_match(), plus two extras. The ovector within the match data block
is used in a different way, and this is described below. The other com-
mon arguments are used in the same way as for pcre2_match(), so their
mon arguments are used in the same way as for pcre2_match(), so their
description is not repeated here.
The two additional arguments provide workspace for the function. The
workspace vector should contain at least 20 elements. It is used for
The two additional arguments provide workspace for the function. The
workspace vector should contain at least 20 elements. It is used for
keeping track of multiple paths through the pattern tree. More
workspace is needed for patterns and subjects where there are a lot of
workspace is needed for patterns and subjects where there are a lot of
potential matches.
Here is an example of a simple call to pcre2_dfa_match():
@ -3606,45 +3613,45 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
Option bits for pcre_dfa_match()
The unused bits of the options argument for pcre2_dfa_match() must be
zero. The only bits that may be set are PCRE2_ANCHORED,
PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO-
The unused bits of the options argument for pcre2_dfa_match() must be
zero. The only bits that may be set are PCRE2_ANCHORED,
PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO-
TEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK,
PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and
PCRE2_DFA_RESTART. All but the last four of these are exactly the same
PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and
PCRE2_DFA_RESTART. All but the last four of these are exactly the same
as for pcre2_match(), so their description is not repeated here.
PCRE2_PARTIAL_HARD
PCRE2_PARTIAL_SOFT
These have the same general effect as they do for pcre2_match(), but
the details are slightly different. When PCRE2_PARTIAL_HARD is set for
pcre2_dfa_match(), it returns PCRE2_ERROR_PARTIAL if the end of the
These have the same general effect as they do for pcre2_match(), but
the details are slightly different. When PCRE2_PARTIAL_HARD is set for
pcre2_dfa_match(), it returns PCRE2_ERROR_PARTIAL if the end of the
subject is reached and there is still at least one matching possibility
that requires additional characters. This happens even if some complete
matches have already been found. When PCRE2_PARTIAL_SOFT is set, the
return code PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL
if the end of the subject is reached, there have been no complete
matches have already been found. When PCRE2_PARTIAL_SOFT is set, the
return code PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL
if the end of the subject is reached, there have been no complete
matches, but there is still at least one matching possibility. The por-
tion of the string that was inspected when the longest partial match
tion of the string that was inspected when the longest partial match
was found is set as the first matching string in both cases. There is a
more detailed discussion of partial and multi-segment matching, with
more detailed discussion of partial and multi-segment matching, with
examples, in the pcre2partial documentation.
PCRE2_DFA_SHORTEST
Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to
Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to
stop as soon as it has found one match. Because of the way the alterna-
tive algorithm works, this is necessarily the shortest possible match
tive algorithm works, this is necessarily the shortest possible match
at the first possible matching point in the subject string.
PCRE2_DFA_RESTART
When pcre2_dfa_match() returns a partial match, it is possible to call
When pcre2_dfa_match() returns a partial match, it is possible to call
it again, with additional subject characters, and have it continue with
the same match. The PCRE2_DFA_RESTART option requests this action; when
it is set, the workspace and wscount options must reference the same
vector as before because data about the match so far is left in them
it is set, the workspace and wscount options must reference the same
vector as before because data about the match so far is left in them
after a partial match. There is more discussion of this facility in the
pcre2partial documentation.
@ -3652,8 +3659,8 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
When pcre2_dfa_match() succeeds, it may have matched more than one sub-
string in the subject. Note, however, that all the matches from one run
of the function start at the same point in the subject. The shorter
matches are all initial substrings of the longer matches. For example,
of the function start at the same point in the subject. The shorter
matches are all initial substrings of the longer matches. For example,
if the pattern
<.*>
@ -3668,80 +3675,80 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
<something> <something else>
<something>
On success, the yield of the function is a number greater than zero,
which is the number of matched substrings. The offsets of the sub-
strings are returned in the ovector, and can be extracted by number in
the same way as for pcre2_match(), but the numbers bear no relation to
any capture groups that may exist in the pattern, because DFA matching
On success, the yield of the function is a number greater than zero,
which is the number of matched substrings. The offsets of the sub-
strings are returned in the ovector, and can be extracted by number in
the same way as for pcre2_match(), but the numbers bear no relation to
any capture groups that may exist in the pattern, because DFA matching
does not support capturing.
Calls to the convenience functions that extract substrings by name re-
Calls to the convenience functions that extract substrings by name re-
turn the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used af-
ter a DFA match. The convenience functions that extract substrings by
ter a DFA match. The convenience functions that extract substrings by
number never return PCRE2_ERROR_NOSUBSTRING.
The matched strings are stored in the ovector in reverse order of
length; that is, the longest matching string is first. If there were
too many matches to fit into the ovector, the yield of the function is
The matched strings are stored in the ovector in reverse order of
length; that is, the longest matching string is first. If there were
too many matches to fit into the ovector, the yield of the function is
zero, and the vector is filled with the longest matches.
NOTE: PCRE2's "auto-possessification" optimization usually applies to
character repeats at the end of a pattern (as well as internally). For
example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA
matching, this means that only one possible match is found. If you re-
NOTE: PCRE2's "auto-possessification" optimization usually applies to
character repeats at the end of a pattern (as well as internally). For
example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA
matching, this means that only one possible match is found. If you re-
ally do want multiple matches in such cases, either use an ungreedy re-
peat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when com-
peat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when com-
piling.
Error returns from pcre2_dfa_match()
The pcre2_dfa_match() function returns a negative number when it fails.
Many of the errors are the same as for pcre2_match(), as described
Many of the errors are the same as for pcre2_match(), as described
above. There are in addition the following errors that are specific to
pcre2_dfa_match():
PCRE2_ERROR_DFA_UITEM
This return is given if pcre2_dfa_match() encounters an item in the
pattern that it does not support, for instance, the use of \C in a UTF
This return is given if pcre2_dfa_match() encounters an item in the
pattern that it does not support, for instance, the use of \C in a UTF
mode or a backreference.
PCRE2_ERROR_DFA_UCOND
This return is given if pcre2_dfa_match() encounters a condition item
This return is given if pcre2_dfa_match() encounters a condition item
that uses a backreference for the condition, or a test for recursion in
a specific capture group. These are not supported.
PCRE2_ERROR_DFA_UINVALID_UTF
This return is given if pcre2_dfa_match() is called for a pattern that
was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for
This return is given if pcre2_dfa_match() is called for a pattern that
was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for
DFA matching.
PCRE2_ERROR_DFA_WSSIZE
This return is given if pcre2_dfa_match() runs out of space in the
This return is given if pcre2_dfa_match() runs out of space in the
workspace vector.
PCRE2_ERROR_DFA_RECURSE
When a recursion or subroutine call is processed, the matching function
calls itself recursively, using private memory for the ovector and
workspace. This error is given if the internal ovector is not large
enough. This should be extremely rare, as a vector of size 1000 is
calls itself recursively, using private memory for the ovector and
workspace. This error is given if the internal ovector is not large
enough. This should be extremely rare, as a vector of size 1000 is
used.
PCRE2_ERROR_DFA_BADRESTART
When pcre2_dfa_match() is called with the PCRE2_DFA_RESTART option,
some plausibility checks are made on the contents of the workspace,
which should contain data about the previous partial match. If any of
When pcre2_dfa_match() is called with the PCRE2_DFA_RESTART option,
some plausibility checks are made on the contents of the workspace,
which should contain data about the previous partial match. If any of
these checks fail, this error is given.
SEE ALSO
pcre2build(3), pcre2callout(3), pcre2demo(3), pcre2matching(3),
pcre2build(3), pcre2callout(3), pcre2demo(3), pcre2matching(3),
pcre2partial(3), pcre2posix(3), pcre2sample(3), pcre2unicode(3).
@ -3754,7 +3761,7 @@ AUTHOR
REVISION
Last updated: 22 January 2020
Last updated: 16 February 2020
Copyright (c) 1997-2020 University of Cambridge.
------------------------------------------------------------------------------