FCL/sf/os/fshell: comparison libraries/spcre/libpcre/pcre/doc/pcretest.1

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+:7f656887cf89
+.TH PCRETEST 1
+.SH NAME
+pcretest - a program for testing Perl-compatible regular expressions.
+.SH SYNOPSIS
+.rs
+.sp
+.B pcretest "[options] [source] [destination]"
+.sp
+\fBpcretest\fP was written as a test program for the PCRE regular expression
+library itself, but it can also be used for experimenting with regular
+expressions. This document describes the features of the test program; for
+details of the regular expressions themselves, see the
+.\" HREF
+\fBpcrepattern\fP
+.\"
+documentation. For details of the PCRE library function calls and their
+options, see the
+.\" HREF
+\fBpcreapi\fP
+.\"
+documentation.
+.
+.
+.SH OPTIONS
+.rs
+.TP 10
+\fB-b\fP
+Behave as if each regex has the \fB/B\fP (show bytecode) modifier; the internal
+form is output after compilation.
+.TP 10
+\fB-C\fP
+Output the version number of the PCRE library, and all available information
+about the optional features that are included, and then exit.
+.TP 10
+\fB-d\fP
+Behave as if each regex has the \fB/D\fP (debug) modifier; the internal
+form and information about the compiled pattern is output after compilation;
+\fB-d\fP is equivalent to \fB-b -i\fP.
+.TP 10
+\fB-dfa\fP
+Behave as if each data line contains the \eD escape sequence; this causes the
+alternative matching function, \fBpcre_dfa_exec()\fP, to be used instead of the
+standard \fBpcre_exec()\fP function (more detail is given below).
+.TP 10
+\fB-help\fP
+Output a brief summary these options and then exit.
+.TP 10
+\fB-i\fP
+Behave as if each regex has the \fB/I\fP modifier; information about the
+compiled pattern is given after compilation.
+.TP 10
+\fB-m\fP
+Output the size of each compiled pattern after it has been compiled. This is
+equivalent to adding \fB/M\fP to each regular expression. For compatibility
+with earlier versions of pcretest, \fB-s\fP is a synonym for \fB-m\fP.
+.TP 10
+\fB-o\fP \fIosize\fP
+Set the number of elements in the output vector that is used when calling
+\fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP to be \fIosize\fP. The default value
+is 45, which is enough for 14 capturing subexpressions for \fBpcre_exec()\fP or
+22 different matches for \fBpcre_dfa_exec()\fP. The vector size can be
+changed for individual matching calls by including \eO in the data line (see
+below).
+.TP 10
+\fB-p\fP
+Behave as if each regex has the \fB/P\fP modifier; the POSIX wrapper API is
+used to call PCRE. None of the other options has any effect when \fB-p\fP is
+set.
+.TP 10
+\fB-q\fP
+Do not output the version number of \fBpcretest\fP at the start of execution.
+.TP 10
+\fB-S\fP \fIsize\fP
+On Unix-like systems, set the size of the runtime stack to \fIsize\fP
+megabytes.
+.TP 10
+\fB-t\fP
+Run each compile, study, and match many times with a timer, and output
+resulting time per compile or match (in milliseconds). Do not set \fB-m\fP with
+\fB-t\fP, because you will then get the size output a zillion times, and the
+timing will be distorted. You can control the number of iterations that are
+used for timing by following \fB-t\fP with a number (as a separate item on the
+command line). For example, "-t 1000" would iterate 1000 times. The default is
+to iterate 500000 times.
+.TP 10
+\fB-tm\fP
+This is like \fB-t\fP except that it times only the matching phase, not the
+compile or study phases.
+.
+.
+.SH DESCRIPTION
+.rs
+.sp
+If \fBpcretest\fP is given two filename arguments, it reads from the first and
+writes to the second. If it is given only one filename argument, it reads from
+that file and writes to stdout. Otherwise, it reads from stdin and writes to
+stdout, and prompts for each line of input, using "re>" to prompt for regular
+expressions, and "data>" to prompt for data lines.
+.P
+When \fBpcretest\fP is built, a configuration option can specify that it should
+be linked with the \fBlibreadline\fP library. When this is done, if the input
+is from a terminal, it is read using the \fBreadline()\fP function. This
+provides line-editing and history facilities. The output from the \fB-help\fP
+option states whether or not \fBreadline()\fP will be used.
+.P
+The program handles any number of sets of input on a single input file. Each
+set starts with a regular expression, and continues with any number of data
+lines to be matched against the pattern.
+.P
+Each data 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 data lines; the input
+buffer is automatically extended if it is too small.
+.P
+An empty line signals the end of the data lines, at which point a new regular
+expression is read. The regular expressions are given enclosed in any
+non-alphanumeric delimiters other than backslash, for example:
+.sp
+/(a|bc)x+yz/
+.sp
+White space before the initial delimiter is ignored. A regular expression may
+be continued over several input lines, in which case the newline characters are
+included within it. It is possible to include the delimiter within the pattern
+by escaping it, for example
+.sp
+/abc\e/def/
+.sp
+If you do so, the escape and the delimiter form part of the pattern, but since
+delimiters are always non-alphanumeric, this does not affect its interpretation.
+If the terminating delimiter is immediately followed by a backslash, for
+example,
+.sp
+/abc/\e
+.sp
+then a backslash is added to the end of the pattern. This is done to provide a
+way of testing the error condition that arises if a pattern finishes with a
+backslash, because
+.sp
+/abc\e/
+.sp
+is interpreted as the first line of a pattern that starts with "abc/", causing
+pcretest to read the next line as a continuation of the regular expression.
+.
+.
+.SH "PATTERN MODIFIERS"
+.rs
+.sp
+A pattern may be followed by any number of modifiers, which are mostly single
+characters. Following Perl usage, these are referred to below as, for example,
+"the \fB/i\fP modifier", even though the delimiter of the pattern need not
+always be a slash, and no slash is used when writing modifiers. Whitespace may
+appear between the final pattern delimiter and the first modifier, and between
+the modifiers themselves.
+.P
+The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS,
+PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
+\fBpcre_compile()\fP is called. These four modifier letters have the same
+effect as they do in Perl. For example:
+.sp
+/caseless/i
+.sp
+The following table shows additional modifiers for setting PCRE options that do
+not correspond to anything in Perl:
+.sp
+\fB/A\fP              PCRE_ANCHORED
+\fB/C\fP              PCRE_AUTO_CALLOUT
+\fB/E\fP              PCRE_DOLLAR_ENDONLY
+\fB/f\fP              PCRE_FIRSTLINE
+\fB/J\fP              PCRE_DUPNAMES
+\fB/N\fP              PCRE_NO_AUTO_CAPTURE
+\fB/U\fP              PCRE_UNGREEDY
+\fB/X\fP              PCRE_EXTRA
+\fB/<JS>\fP           PCRE_JAVASCRIPT_COMPAT
+\fB/<cr>\fP           PCRE_NEWLINE_CR
+\fB/<lf>\fP           PCRE_NEWLINE_LF
+\fB/<crlf>\fP         PCRE_NEWLINE_CRLF
+\fB/<anycrlf>\fP      PCRE_NEWLINE_ANYCRLF
+\fB/<any>\fP          PCRE_NEWLINE_ANY
+\fB/<bsr_anycrlf>\fP  PCRE_BSR_ANYCRLF
+\fB/<bsr_unicode>\fP  PCRE_BSR_UNICODE
+.sp
+Those specifying line ending sequences are literal strings as shown, but the
+letters can be in either case. This example sets multiline matching with CRLF
+as the line ending sequence:
+.sp
+/^abc/m<crlf>
+.sp
+Details of the meanings of these PCRE options are given in the
+.\" HREF
+\fBpcreapi\fP
+.\"
+documentation.
+.
+.
+.SS "Finding all matches in a string"
+.rs
+.sp
+Searching for all possible matches within each subject string can be requested
+by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
+again to search the remainder of the subject string. The difference between
+\fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
+\fBpcre_exec()\fP to start searching at a new point within the entire string
+(which is in effect what Perl does), whereas the latter passes over a shortened
+substring. This makes a difference to the matching process if the pattern
+begins with a lookbehind assertion (including \eb or \eB).
+.P
+If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches an
+empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
+flags set in order to search for another, non-empty, match at the same point.
+If this second match fails, the start offset is advanced by one, and the normal
+match is retried. This imitates the way Perl handles such cases when using the
+\fB/g\fP modifier or the \fBsplit()\fP function.
+.
+.
+.SS "Other modifiers"
+.rs
+.sp
+There are yet more modifiers for controlling the way \fBpcretest\fP
+operates.
+.P
+The \fB/+\fP modifier requests that as well as outputting the substring that
+matched the entire pattern, pcretest should in addition output the remainder of
+the subject string. This is useful for tests where the subject contains
+multiple copies of the same substring.
+.P
+The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP
+output a representation of the compiled byte code after compilation. Normally
+this information contains length and offset values; however, if \fB/Z\fP is
+also present, this data is replaced by spaces. This is a special feature for
+use in the automatic test scripts; it ensures that the same output is generated
+for different internal link sizes.
+.P
+The \fB/L\fP modifier must be followed directly by the name of a locale, for
+example,
+.sp
+/pattern/Lfr_FR
+.sp
+For this reason, it must be the last modifier. The given locale is set,
+\fBpcre_maketables()\fP is called to build a set of character tables for the
+locale, and this is then passed to \fBpcre_compile()\fP when compiling the
+regular expression. Without an \fB/L\fP modifier, NULL is passed as the tables
+pointer; that is, \fB/L\fP applies only to the expression on which it appears.
+.P
+The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
+compiled pattern (whether it is anchored, has a fixed first character, and
+so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
+pattern. If the pattern is studied, the results of that are also output.
+.P
+The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to
+\fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers.
+.P
+The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
+fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
+facility is for testing the feature in PCRE that allows it to execute patterns
+that were compiled on a host with a different endianness. This feature is not
+available when the POSIX interface to PCRE is being used, that is, when the
+\fB/P\fP pattern modifier is specified. See also the section about saving and
+reloading compiled patterns below.
+.P
+The \fB/S\fP modifier causes \fBpcre_study()\fP to be called after the
+expression has been compiled, and the results used when the expression is
+matched.
+.P
+The \fB/M\fP modifier causes the size of memory block used to hold the compiled
+pattern to be output.
+.P
+The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
+API rather than its native API. When this is done, all other modifiers except
+\fB/i\fP, \fB/m\fP, and \fB/+\fP are ignored. REG_ICASE is set if \fB/i\fP is
+present, and REG_NEWLINE is set if \fB/m\fP is present. The wrapper functions
+force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
+.P
+The \fB/8\fP modifier causes \fBpcretest\fP to call PCRE with the PCRE_UTF8
+option set. This turns on support for UTF-8 character handling in PCRE,
+provided that it was compiled with this support enabled. This modifier also
+causes any non-printing characters in output strings to be printed using the
+\ex{hh...} notation if they are valid UTF-8 sequences.
+.P
+If the \fB/?\fP modifier is used with \fB/8\fP, it causes \fBpcretest\fP to
+call \fBpcre_compile()\fP with the PCRE_NO_UTF8_CHECK option, to suppress the
+checking of the string for UTF-8 validity.
+.
+.
+.SH "DATA LINES"
+.rs
+.sp
+Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
+whitespace is removed, and it is then scanned for \e escapes. Some of these are
+pretty esoteric features, intended for checking out some of the more
+complicated features of PCRE. If you are just testing "ordinary" regular
+expressions, you probably don't need any of these. The following escapes are
+recognized:
+.sp
+\ea         alarm (BEL, \ex07)
+\eb         backspace (\ex08)
+\ee         escape (\ex27)
+\ef         formfeed (\ex0c)
+\en         newline (\ex0a)
+.\" JOIN
+\eqdd       set the PCRE_MATCH_LIMIT limit to dd
+(any number of digits)
+\er         carriage return (\ex0d)
+\et         tab (\ex09)
+\ev         vertical tab (\ex0b)
+\ennn       octal character (up to 3 octal digits)
+\exhh       hexadecimal character (up to 2 hex digits)
+.\" JOIN
+\ex{hh...}  hexadecimal character, any number of digits
+in UTF-8 mode
+.\" JOIN
+\eA         pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\eB         pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\eCdd       call pcre_copy_substring() for substring dd
+after a successful match (number less than 32)
+.\" JOIN
+\eCname     call pcre_copy_named_substring() for substring
+"name" after a successful match (name termin-
+ated by next non alphanumeric character)
+.\" JOIN
+\eC+        show the current captured substrings at callout
+time
+\eC-        do not supply a callout function
+.\" JOIN
+\eC!n       return 1 instead of 0 when callout number n is
+reached
+.\" JOIN
+\eC!n!m     return 1 instead of 0 when callout number n is
+reached for the nth time
+.\" JOIN
+\eC*n       pass the number n (may be negative) as callout
+data; this is used as the callout return value
+\eD         use the \fBpcre_dfa_exec()\fP match function
+\eF         only shortest match for \fBpcre_dfa_exec()\fP
+.\" JOIN
+\eGdd       call pcre_get_substring() for substring dd
+after a successful match (number less than 32)
+.\" JOIN
+\eGname     call pcre_get_named_substring() for substring
+"name" after a successful match (name termin-
+ated by next non-alphanumeric character)
+.\" JOIN
+\eL         call pcre_get_substringlist() after a
+successful match
+.\" JOIN
+\eM         discover the minimum MATCH_LIMIT and
+MATCH_LIMIT_RECURSION settings
+.\" JOIN
+\eN         pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\eOdd       set the size of the output vector passed to
+\fBpcre_exec()\fP to dd (any number of digits)
+.\" JOIN
+\eP         pass the PCRE_PARTIAL option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\eQdd       set the PCRE_MATCH_LIMIT_RECURSION limit to dd
+(any number of digits)
+\eR         pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
+\eS         output details of memory get/free calls during matching
+.\" JOIN
+\eZ         pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\e?         pass the PCRE_NO_UTF8_CHECK option to
+\fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
+\e>dd       start the match at offset dd (any number of digits);
+.\" JOIN
+this sets the \fIstartoffset\fP argument for \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\e<cr>      pass the PCRE_NEWLINE_CR option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\e<lf>      pass the PCRE_NEWLINE_LF option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\e<crlf>    pass the PCRE_NEWLINE_CRLF option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.\" JOIN
+\e<any>     pass the PCRE_NEWLINE_ANY option to \fBpcre_exec()\fP
+or \fBpcre_dfa_exec()\fP
+.sp
+The escapes that specify line ending sequences are literal strings, exactly as
+shown. No more than one newline setting should be present in any data line.
+.P
+A backslash followed by anything else just escapes the anything else. If
+the very last character is a backslash, it is ignored. This gives a way of
+passing an empty line as data, since a real empty line terminates the data
+input.
+.P
+If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
+different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP
+fields of the \fBpcre_extra\fP data structure, until it finds the minimum
+numbers for each parameter that allow \fBpcre_exec()\fP to complete. The
+\fImatch_limit\fP number is a measure of the amount of backtracking that takes
+place, and checking it out can be instructive. For most simple matches, the
+number is quite small, but for patterns with very large numbers of matching
+possibilities, it can become large very quickly with increasing length of
+subject string. The \fImatch_limit_recursion\fP number is a measure of how much
+stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
+to complete the match attempt.
+.P
+When \eO is used, the value specified may be higher or lower than the size set
+by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
+the call of \fBpcre_exec()\fP for the line in which it appears.
+.P
+If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
+API to be used, the only option-setting sequences that have any effect are \eB
+and \eZ, causing REG_NOTBOL and REG_NOTEOL, respectively, to be passed to
+\fBregexec()\fP.
+.P
+The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
+of the \fB/8\fP modifier on the pattern. It is recognized always. There may be
+any number of hexadecimal digits inside the braces. The result is from one to
+six bytes, encoded according to the original UTF-8 rules of RFC 2279. This
+allows for values in the range 0 to 0x7FFFFFFF. Note that not all of those are
+valid Unicode code points, or indeed valid UTF-8 characters according to the
+later rules in RFC 3629.
+.
+.
+.SH "THE ALTERNATIVE MATCHING FUNCTION"
+.rs
+.sp
+By default, \fBpcretest\fP uses the standard PCRE matching function,
+\fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
+alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
+different way, and has some restrictions. The differences between the two
+functions are described in the
+.\" HREF
+\fBpcrematching\fP
+.\"
+documentation.
+.P
+If a data line contains the \eD escape sequence, or if the command line
+contains the \fB-dfa\fP option, the alternative matching function is called.
+This function finds all possible matches at a given point. If, however, the \eF
+escape sequence is present in the data line, it stops after the first match is
+found. This is always the shortest possible match.
+.
+.
+.SH "DEFAULT OUTPUT FROM PCRETEST"
+.rs
+.sp
+This section describes the output when the normal matching function,
+\fBpcre_exec()\fP, is being used.
+.P
+When a match succeeds, pcretest outputs the list of captured substrings that
+\fBpcre_exec()\fP returns, starting with number 0 for the string that matched
+the whole pattern. Otherwise, it outputs "No match" or "Partial match"
+when \fBpcre_exec()\fP returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PARTIAL,
+respectively, and otherwise the PCRE negative error number. Here is an example
+of an interactive \fBpcretest\fP run.
+.sp
+$ pcretest
+PCRE version 7.0 30-Nov-2006
+.sp
+re> /^abc(\ed+)/
+data> abc123
+0: abc123
+1: 123
+data> xyz
+No match
+.sp
+Note that unset capturing substrings that are not followed by one that is set
+are not returned by \fBpcre_exec()\fP, and are not shown by \fBpcretest\fP. 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.
+.sp
+re> /(a)|(b)/
+data> a
+0: a
+1: a
+data> b
+0: b
+1: <unset>
+2: b
+.sp
+If the strings contain any non-printing characters, they are output as \e0x
+escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
+pattern. See below for the definition of non-printing characters. If the
+pattern has the \fB/+\fP modifier, the output for substring 0 is followed by
+the the rest of the subject string, identified by "0+" like this:
+.sp
+re> /cat/+
+data> cataract
+0: cat
+0+ aract
+.sp
+If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
+matching attempts are output in sequence, like this:
+.sp
+re> /\eBi(\ew\ew)/g
+data> Mississippi
+0: iss
+1: ss
+0: iss
+1: ss
+0: ipp
+1: pp
+.sp
+"No match" is output only if the first match attempt fails.
+.P
+If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a
+data line that is successfully matched, the substrings extracted by the
+convenience functions are output with C, G, or L after the string number
+instead of a colon. This is in addition to the normal full list. The string
+length (that is, the return from the extraction function) is given in
+parentheses after each string for \fB\eC\fP and \fB\eG\fP.
+.P
+Note that whereas patterns can be continued over several lines (a plain ">"
+prompt is used for continuations), data lines may not. However newlines can be
+included in data by means of the \en escape (or \er, \er\en, etc., depending on
+the newline sequence setting).
+.
+.
+.
+.SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION"
+.rs
+.sp
+When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
+means of the \eD escape sequence or the \fB-dfa\fP command line option), the
+output consists of a list of all the matches that start at the first point in
+the subject where there is at least one match. For example:
+.sp
+re> /(tang|tangerine|tan)/
+data> yellow tangerine\eD
+0: tangerine
+1: tang
+2: tan
+.sp
+(Using the normal matching function on this data finds only "tang".) The
+longest matching string is always given first (and numbered zero).
+.P
+If \fB/g\fP is present on the pattern, the search for further matches resumes
+at the end of the longest match. For example:
+.sp
+re> /(tang|tangerine|tan)/g
+data> yellow tangerine and tangy sultana\eD
+0: tangerine
+1: tang
+2: tan
+0: tang
+1: tan
+0: tan
+.sp
+Since the matching function does not support substring capture, the escape
+sequences that are concerned with captured substrings are not relevant.
+.
+.
+.SH "RESTARTING AFTER A PARTIAL MATCH"
+.rs
+.sp
+When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
+indicating that the subject partially matched the pattern, you can restart the
+match with additional subject data by means of the \eR escape sequence. For
+example:
+.sp
+re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
+data> 23ja\eP\eD
+Partial match: 23ja
+data> n05\eR\eD
+0: n05
+.sp
+For further information about partial matching, see the
+.\" HREF
+\fBpcrepartial\fP
+.\"
+documentation.
+.
+.
+.SH CALLOUTS
+.rs
+.sp
+If the pattern contains any callout requests, \fBpcretest\fP's callout function
+is called during matching. This works with both matching functions. By default,
+the called function displays the callout number, the start and current
+positions in the text at the callout time, and the next pattern item to be
+tested. For example, the output
+.sp
+--->pqrabcdef
+0    ^  ^     \ed
+.sp
+indicates that callout number 0 occurred for a match attempt starting at the
+fourth character of the subject string, when the pointer was at the seventh
+character of the data, and when the next pattern item was \ed. Just one
+circumflex is output if the start and current positions are the same.
+.P
+Callouts numbered 255 are assumed to be automatic callouts, inserted as a
+result of the \fB/C\fP pattern modifier. In this case, instead of showing the
+callout number, the offset in the pattern, preceded by a plus, is output. For
+example:
+.sp
+re> /\ed?[A-E]\e*/C
+data> E*
+--->E*
++0 ^      \ed?
++3 ^      [A-E]
++8 ^^     \e*
++10 ^ ^
+0: E*
+.sp
+The callout function in \fBpcretest\fP returns zero (carry on matching) by
+default, but you can use a \eC item in a data line (as described above) to
+change this.
+.P
+Inserting callouts can be helpful when using \fBpcretest\fP to check
+complicated regular expressions. For further information about callouts, see
+the
+.\" HREF
+\fBpcrecallout\fP
+.\"
+documentation.
+.
+.
+.
+.SH "NON-PRINTING CHARACTERS"
+.rs
+.sp
+When \fBpcretest\fP is outputting text in the compiled version of a pattern,
+bytes other than 32-126 are always treated as non-printing characters are are
+therefore shown as hex escapes.
+.P
+When \fBpcretest\fP 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 \fB/L\fP modifier). In this case, the \fBisprint()\fP
+function to distinguish printing and non-printing characters.
+.
+.
+.
+.SH "SAVING AND RELOADING COMPILED PATTERNS"
+.rs
+.sp
+The facilities described in this section are not available when the POSIX
+inteface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
+specified.
+.P
+When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
+compiled pattern to a file, by following the modifiers with > and a file name.
+For example:
+.sp
+/pattern/im >/some/file
+.sp
+See the
+.\" HREF
+\fBpcreprecompile\fP
+.\"
+documentation for a discussion about saving and re-using compiled patterns.
+.P
+The data that is written is binary. The first eight bytes are the length of the
+compiled pattern data followed by the length of the optional study data, each
+written as four bytes in big-endian order (most significant byte first). If
+there is no study data (either the pattern was not studied, or studying did not
+return any data), the second length is zero. The lengths are followed by an
+exact copy of the compiled pattern. If there is additional study data, this
+follows immediately after the compiled pattern. After writing the file,
+\fBpcretest\fP expects to read a new pattern.
+.P
+A saved pattern can be reloaded into \fBpcretest\fP by specifing < and a file
+name instead of a pattern. The name of the file must not contain a < character,
+as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
+characters.
+For example:
+.sp
+re> </some/file
+Compiled regex loaded from /some/file
+No study data
+.sp
+When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
+the usual way.
+.P
+You can copy a file written by \fBpcretest\fP to a different host and reload it
+there, even if the new host has opposite endianness to the one on which the
+pattern was compiled. For example, you can compile on an i86 machine and run on
+a SPARC machine.
+.P
+File names for saving and reloading can be absolute or relative, but note that
+the shell facility of expanding a file name that starts with a tilde (~) is not
+available.
+.P
+The ability to save and reload files in \fBpcretest\fP is intended for testing
+and experimentation. It is not intended for production use because only a
+single pattern can be written to a file. Furthermore, there is no facility for
+supplying custom character tables for use with a reloaded pattern. If the
+original pattern was compiled with custom tables, an attempt to match a subject
+string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
+Finally, if you attempt to load a file that is not in the correct format, the
+result is undefined.
+.
+.
+.SH "SEE ALSO"
+.rs
+.sp
+\fBpcre\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3),
+\fBpcrepartial\fP(d), \fBpcrepattern\fP(3), \fBpcreprecompile\fP(3).
+.
+.
+.SH AUTHOR
+.rs
+.sp
+.nf
+Philip Hazel
+University Computing Service
+Cambridge CB2 3QH, England.
+.fi
+.
+.
+.SH REVISION
+.rs
+.sp
+.nf
+Last updated: 12 April 2008
+Copyright (c) 1997-2008 University of Cambridge.
+.fi