/[pcre]/code/trunk/doc/pcretest.txt
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1 The pcretest program
2 --------------------
3
4 This program is intended for testing PCRE, but it can also be used for
5 experimenting with regular expressions.
6
7 If it is given two filename arguments, it reads from the first and writes to
8 the second. If it is given only one filename argument, it reads from that file
9 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
10 prompts for each line of input, using "re>" to prompt for regular expressions,
11 and "data>" to prompt for data lines.
12
13 The program handles any number of sets of input on a single input file. Each
14 set starts with a regular expression, and continues with any number of data
15 lines to be matched against the pattern. An empty line signals the end of the
16 data lines, at which point a new regular expression is read. The regular
17 expressions are given enclosed in any non-alphameric delimiters other than
18 backslash, for example
19
20 /(a|bc)x+yz/
21
22 White space before the initial delimiter is ignored. A regular expression may
23 be continued over several input lines, in which case the newline characters are
24 included within it. See the test input files in the testdata directory for many
25 examples. It is possible to include the delimiter within the pattern by
26 escaping it, for example
27
28 /abc\/def/
29
30 If you do so, the escape and the delimiter form part of the pattern, but since
31 delimiters are always non-alphameric, this does not affect its interpretation.
32 If the terminating delimiter is immediately followed by a backslash, for
33 example,
34
35 /abc/\
36
37 then a backslash is added to the end of the pattern. This is done to provide a
38 way of testing the error condition that arises if a pattern finishes with a
39 backslash, because
40
41 /abc\/
42
43 is interpreted as the first line of a pattern that starts with "abc/", causing
44 pcretest to read the next line as a continuation of the regular expression.
45
46
47 PATTERN MODIFIERS
48 -----------------
49
50 The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,
51 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
52 example:
53
54 /caseless/i
55
56 These modifier letters have the same effect as they do in Perl. There are
57 others which set PCRE options that do not correspond to anything in Perl: /A,
58 /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
59
60 Searching for all possible matches within each subject string can be requested
61 by the /g or /G modifier. After finding a match, PCRE is called again to search
62 the remainder of the subject string. The difference between /g and /G is that
63 the former uses the startoffset argument to pcre_exec() to start searching at
64 a new point within the entire string (which is in effect what Perl does),
65 whereas the latter passes over a shortened substring. This makes a difference
66 to the matching process if the pattern begins with a lookbehind assertion
67 (including \b or \B).
68
69 If any call to pcre_exec() in a /g or /G sequence matches an empty string, the
70 next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED flags set in order
71 to search for another, non-empty, match at the same point. If this second match
72 fails, the start offset is advanced by one, and the normal match is retried.
73 This imitates the way Perl handles such cases when using the /g modifier or the
74 split() function.
75
76 There are a number of other modifiers for controlling the way pcretest
77 operates.
78
79 The /+ modifier requests that as well as outputting the substring that matched
80 the entire pattern, pcretest should in addition output the remainder of the
81 subject string. This is useful for tests where the subject contains multiple
82 copies of the same substring.
83
84 The /L modifier must be followed directly by the name of a locale, for example,
85
86 /pattern/Lfr
87
88 For this reason, it must be the last modifier letter. The given locale is set,
89 pcre_maketables() is called to build a set of character tables for the locale,
90 and this is then passed to pcre_compile() when compiling the regular
91 expression. Without an /L modifier, NULL is passed as the tables pointer; that
92 is, /L applies only to the expression on which it appears.
93
94 The /I modifier requests that pcretest output information about the compiled
95 expression (whether it is anchored, has a fixed first character, and so on). It
96 does this by calling pcre_fullinfo() after compiling an expression, and
97 outputting the information it gets back. If the pattern is studied, the results
98 of that are also output.
99
100 The /D modifier is a PCRE debugging feature, which also assumes /I. It causes
101 the internal form of compiled regular expressions to be output after
102 compilation.
103
104 The /S modifier causes pcre_study() to be called after the expression has been
105 compiled, and the results used when the expression is matched.
106
107 The /M modifier causes the size of memory block used to hold the compiled
108 pattern to be output.
109
110 The /P modifier causes pcretest to call PCRE via the POSIX wrapper API rather
111 than its native API. When this is done, all other modifiers except /i, /m, and
112 /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
113 is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
114 PCRE_DOTALL unless REG_NEWLINE is set.
115
116 The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option set.
117 This turns on the (currently incomplete) support for UTF-8 character handling
118 in PCRE, provided that it was compiled with this support enabled. This modifier
119 also causes any non-printing characters in output strings to be printed using
120 the \x{hh...} notation if they are valid UTF-8 sequences.
121
122
123 DATA LINES
124 ----------
125
126 Before each data line is passed to pcre_exec(), leading and trailing whitespace
127 is removed, and it is then scanned for \ escapes. The following are recognized:
128
129 \a alarm (= BEL)
130 \b backspace
131 \e escape
132 \f formfeed
133 \n newline
134 \r carriage return
135 \t tab
136 \v vertical tab
137 \nnn octal character (up to 3 octal digits)
138 \xhh hexadecimal character (up to 2 hex digits)
139 \x{hh...} hexadecimal UTF-8 character
140
141 \A pass the PCRE_ANCHORED option to pcre_exec()
142 \B pass the PCRE_NOTBOL option to pcre_exec()
143 \Cdd call pcre_copy_substring() for substring dd after a successful
144 match (any decimal number less than 32)
145 \Gdd call pcre_get_substring() for substring dd after a successful
146 match (any decimal number less than 32)
147 \L call pcre_get_substringlist() after a successful match
148 \N pass the PCRE_NOTEMPTY option to pcre_exec()
149 \Odd set the size of the output vector passed to pcre_exec() to dd
150 (any number of decimal digits)
151 \Z pass the PCRE_NOTEOL option to pcre_exec()
152
153 A backslash followed by anything else just escapes the anything else. If the
154 very last character is a backslash, it is ignored. This gives a way of passing
155 an empty line as data, since a real empty line terminates the data input.
156
157 If /P was present on the regex, causing the POSIX wrapper API to be used, only
158 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
159 regexec() respectively.
160
161 The use of \x{hh...} to represent UTF-8 characters is not dependent on the use
162 of the /8 modifier on the pattern. It is recognized always. There may be any
163 number of hexadecimal digits inside the braces. The result is from one to six
164 bytes, encoded according to the UTF-8 rules.
165
166
167 OUTPUT FROM PCRETEST
168 --------------------
169
170 When a match succeeds, pcretest outputs the list of captured substrings that
171 pcre_exec() returns, starting with number 0 for the string that matched the
172 whole pattern. Here is an example of an interactive pcretest run.
173
174 $ pcretest
175 PCRE version 2.06 08-Jun-1999
176
177 re> /^abc(\d+)/
178 data> abc123
179 0: abc123
180 1: 123
181 data> xyz
182 No match
183
184 If the strings contain any non-printing characters, they are output as \0x
185 escapes, or as \x{...} escapes if the /8 modifier was present on the pattern.
186 If the pattern has the /+ modifier, then the output for substring 0 is followed
187 by the the rest of the subject string, identified by "0+" like this:
188
189 re> /cat/+
190 data> cataract
191 0: cat
192 0+ aract
193
194 If the pattern has the /g or /G modifier, the results of successive matching
195 attempts are output in sequence, like this:
196
197 re> /\Bi(\w\w)/g
198 data> Mississippi
199 0: iss
200 1: ss
201 0: iss
202 1: ss
203 0: ipp
204 1: pp
205
206 "No match" is output only if the first match attempt fails.
207
208 If any of \C, \G, or \L are present in a data line that is successfully
209 matched, the substrings extracted by the convenience functions are output with
210 C, G, or L after the string number instead of a colon. This is in addition to
211 the normal full list. The string length (that is, the return from the
212 extraction function) is given in parentheses after each string for \C and \G.
213
214 Note that while patterns can be continued over several lines (a plain ">"
215 prompt is used for continuations), data lines may not. However newlines can be
216 included in data by means of the \n escape.
217
218
219 COMMAND LINE OPTIONS
220 --------------------
221
222 If the -p option is given to pcretest, it is equivalent to adding /P to each
223 regular expression: the POSIX wrapper API is used to call PCRE. None of the
224 following flags has any effect in this case.
225
226 If the option -d is given to pcretest, it is equivalent to adding /D to each
227 regular expression: the internal form is output after compilation.
228
229 If the option -i is given to pcretest, it is equivalent to adding /I to each
230 regular expression: information about the compiled pattern is given after
231 compilation.
232
233 If the option -m is given to pcretest, it outputs the size of each compiled
234 pattern after it has been compiled. It is equivalent to adding /M to each
235 regular expression. For compatibility with earlier versions of pcretest, -s is
236 a synonym for -m.
237
238 If the -t option is given, each compile, study, and match is run 20000 times
239 while being timed, and the resulting time per compile or match is output in
240 milliseconds. Do not set -t with -m, because you will then get the size output
241 20000 times and the timing will be distorted. If you want to change the number
242 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
243 pcretest.c
244
245 Philip Hazel <ph10@cam.ac.uk>
246 August 2000

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