Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1 | :mod:`shlex` --- Simple lexical analysis |
| 2 | ======================================== |
| 3 | |
| 4 | .. module:: shlex |
| 5 | :synopsis: Simple lexical analysis for Unix shell-like languages. |
| 6 | .. moduleauthor:: Eric S. Raymond <esr@snark.thyrsus.com> |
| 7 | .. moduleauthor:: Gustavo Niemeyer <niemeyer@conectiva.com> |
| 8 | .. sectionauthor:: Eric S. Raymond <esr@snark.thyrsus.com> |
| 9 | .. sectionauthor:: Gustavo Niemeyer <niemeyer@conectiva.com> |
| 10 | |
Raymond Hettinger | a199368 | 2011-01-27 01:20:32 +0000 | [diff] [blame] | 11 | **Source code:** :source:`Lib/shlex.py` |
| 12 | |
| 13 | -------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 14 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 15 | The :class:`shlex` class makes it easy to write lexical analyzers for simple |
| 16 | syntaxes resembling that of the Unix shell. This will often be useful for |
| 17 | writing minilanguages, (for example, in run control files for Python |
| 18 | applications) or for parsing quoted strings. |
| 19 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 20 | The :mod:`shlex` module defines the following functions: |
| 21 | |
| 22 | |
Georg Brandl | 1824415 | 2009-09-02 20:34:52 +0000 | [diff] [blame] | 23 | .. function:: split(s, comments=False, posix=True) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 24 | |
| 25 | Split the string *s* using shell-like syntax. If *comments* is :const:`False` |
| 26 | (the default), the parsing of comments in the given string will be disabled |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 27 | (setting the :attr:`commenters` attribute of the :class:`shlex` instance to |
| 28 | the empty string). This function operates in POSIX mode by default, but uses |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 29 | non-POSIX mode if the *posix* argument is false. |
| 30 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 31 | .. note:: |
| 32 | |
Georg Brandl | 1824415 | 2009-09-02 20:34:52 +0000 | [diff] [blame] | 33 | Since the :func:`split` function instantiates a :class:`shlex` instance, |
| 34 | passing ``None`` for *s* will read the string to split from standard |
| 35 | input. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 36 | |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 37 | |
| 38 | .. function:: quote(s) |
| 39 | |
| 40 | Return a shell-escaped version of the string *s*. The returned value is a |
Éric Araujo | 30e277b | 2011-07-29 15:08:42 +0200 | [diff] [blame] | 41 | string that can safely be used as one token in a shell command line, for |
| 42 | cases where you cannot use a list. |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 43 | |
Éric Araujo | 30e277b | 2011-07-29 15:08:42 +0200 | [diff] [blame] | 44 | This idiom would be unsafe:: |
| 45 | |
| 46 | >>> filename = 'somefile; rm -rf ~' |
| 47 | >>> command = 'ls -l {}'.format(filename) |
| 48 | >>> print(command) # executed by a shell: boom! |
| 49 | ls -l somefile; rm -rf ~ |
| 50 | |
| 51 | :func:`quote` lets you plug the security hole:: |
| 52 | |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 53 | >>> command = 'ls -l {}'.format(quote(filename)) |
| 54 | >>> print(command) |
Éric Araujo | 30e277b | 2011-07-29 15:08:42 +0200 | [diff] [blame] | 55 | ls -l 'somefile; rm -rf ~' |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 56 | >>> remote_command = 'ssh home {}'.format(quote(command)) |
| 57 | >>> print(remote_command) |
Éric Araujo | 30e277b | 2011-07-29 15:08:42 +0200 | [diff] [blame] | 58 | ssh home 'ls -l '"'"'somefile; rm -rf ~'"'"'' |
| 59 | |
| 60 | The quoting is compatible with UNIX shells and with :func:`split`: |
| 61 | |
| 62 | >>> remote_command = split(remote_command) |
| 63 | >>> remote_command |
| 64 | ['ssh', 'home', "ls -l 'somefile; rm -rf ~'"] |
| 65 | >>> command = split(remote_command[-1]) |
| 66 | >>> command |
| 67 | ['ls', '-l', 'somefile; rm -rf ~'] |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 68 | |
Eli Bendersky | 493846e | 2012-03-01 19:07:55 +0200 | [diff] [blame] | 69 | .. versionadded:: 3.3 |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 70 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 71 | The :mod:`shlex` module defines the following class: |
| 72 | |
| 73 | |
Georg Brandl | 1824415 | 2009-09-02 20:34:52 +0000 | [diff] [blame] | 74 | .. class:: shlex(instream=None, infile=None, posix=False) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 75 | |
| 76 | A :class:`shlex` instance or subclass instance is a lexical analyzer object. |
| 77 | The initialization argument, if present, specifies where to read characters |
| 78 | from. It must be a file-/stream-like object with :meth:`read` and |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 79 | :meth:`readline` methods, or a string. If no argument is given, input will |
| 80 | be taken from ``sys.stdin``. The second optional argument is a filename |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 81 | string, which sets the initial value of the :attr:`infile` attribute. If the |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 82 | *instream* argument is omitted or equal to ``sys.stdin``, this second |
| 83 | argument defaults to "stdin". The *posix* argument defines the operational |
| 84 | mode: when *posix* is not true (default), the :class:`shlex` instance will |
| 85 | operate in compatibility mode. When operating in POSIX mode, :class:`shlex` |
| 86 | will try to be as close as possible to the POSIX shell parsing rules. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 87 | |
| 88 | |
| 89 | .. seealso:: |
| 90 | |
Alexandre Vassalotti | 1d1eaa4 | 2008-05-14 22:59:42 +0000 | [diff] [blame] | 91 | Module :mod:`configparser` |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 92 | Parser for configuration files similar to the Windows :file:`.ini` files. |
| 93 | |
| 94 | |
| 95 | .. _shlex-objects: |
| 96 | |
| 97 | shlex Objects |
| 98 | ------------- |
| 99 | |
| 100 | A :class:`shlex` instance has the following methods: |
| 101 | |
| 102 | |
| 103 | .. method:: shlex.get_token() |
| 104 | |
| 105 | Return a token. If tokens have been stacked using :meth:`push_token`, pop a |
| 106 | token off the stack. Otherwise, read one from the input stream. If reading |
| 107 | encounters an immediate end-of-file, :attr:`self.eof` is returned (the empty |
| 108 | string (``''``) in non-POSIX mode, and ``None`` in POSIX mode). |
| 109 | |
| 110 | |
| 111 | .. method:: shlex.push_token(str) |
| 112 | |
| 113 | Push the argument onto the token stack. |
| 114 | |
| 115 | |
| 116 | .. method:: shlex.read_token() |
| 117 | |
| 118 | Read a raw token. Ignore the pushback stack, and do not interpret source |
| 119 | requests. (This is not ordinarily a useful entry point, and is documented here |
| 120 | only for the sake of completeness.) |
| 121 | |
| 122 | |
| 123 | .. method:: shlex.sourcehook(filename) |
| 124 | |
| 125 | When :class:`shlex` detects a source request (see :attr:`source` below) this |
| 126 | method is given the following token as argument, and expected to return a tuple |
| 127 | consisting of a filename and an open file-like object. |
| 128 | |
| 129 | Normally, this method first strips any quotes off the argument. If the result |
| 130 | is an absolute pathname, or there was no previous source request in effect, or |
| 131 | the previous source was a stream (such as ``sys.stdin``), the result is left |
| 132 | alone. Otherwise, if the result is a relative pathname, the directory part of |
| 133 | the name of the file immediately before it on the source inclusion stack is |
| 134 | prepended (this behavior is like the way the C preprocessor handles ``#include |
| 135 | "file.h"``). |
| 136 | |
| 137 | The result of the manipulations is treated as a filename, and returned as the |
| 138 | first component of the tuple, with :func:`open` called on it to yield the second |
| 139 | component. (Note: this is the reverse of the order of arguments in instance |
| 140 | initialization!) |
| 141 | |
| 142 | This hook is exposed so that you can use it to implement directory search paths, |
| 143 | addition of file extensions, and other namespace hacks. There is no |
| 144 | corresponding 'close' hook, but a shlex instance will call the :meth:`close` |
| 145 | method of the sourced input stream when it returns EOF. |
| 146 | |
| 147 | For more explicit control of source stacking, use the :meth:`push_source` and |
| 148 | :meth:`pop_source` methods. |
| 149 | |
| 150 | |
Georg Brandl | 1824415 | 2009-09-02 20:34:52 +0000 | [diff] [blame] | 151 | .. method:: shlex.push_source(newstream, newfile=None) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 152 | |
| 153 | Push an input source stream onto the input stack. If the filename argument is |
| 154 | specified it will later be available for use in error messages. This is the |
| 155 | same method used internally by the :meth:`sourcehook` method. |
| 156 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 157 | |
| 158 | .. method:: shlex.pop_source() |
| 159 | |
| 160 | Pop the last-pushed input source from the input stack. This is the same method |
| 161 | used internally when the lexer reaches EOF on a stacked input stream. |
| 162 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 163 | |
Georg Brandl | 1824415 | 2009-09-02 20:34:52 +0000 | [diff] [blame] | 164 | .. method:: shlex.error_leader(infile=None, lineno=None) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 165 | |
| 166 | This method generates an error message leader in the format of a Unix C compiler |
| 167 | error label; the format is ``'"%s", line %d: '``, where the ``%s`` is replaced |
| 168 | with the name of the current source file and the ``%d`` with the current input |
| 169 | line number (the optional arguments can be used to override these). |
| 170 | |
| 171 | This convenience is provided to encourage :mod:`shlex` users to generate error |
| 172 | messages in the standard, parseable format understood by Emacs and other Unix |
| 173 | tools. |
| 174 | |
| 175 | Instances of :class:`shlex` subclasses have some public instance variables which |
| 176 | either control lexical analysis or can be used for debugging: |
| 177 | |
| 178 | |
| 179 | .. attribute:: shlex.commenters |
| 180 | |
| 181 | The string of characters that are recognized as comment beginners. All |
| 182 | characters from the comment beginner to end of line are ignored. Includes just |
| 183 | ``'#'`` by default. |
| 184 | |
| 185 | |
| 186 | .. attribute:: shlex.wordchars |
| 187 | |
| 188 | The string of characters that will accumulate into multi-character tokens. By |
| 189 | default, includes all ASCII alphanumerics and underscore. |
| 190 | |
| 191 | |
| 192 | .. attribute:: shlex.whitespace |
| 193 | |
| 194 | Characters that will be considered whitespace and skipped. Whitespace bounds |
| 195 | tokens. By default, includes space, tab, linefeed and carriage-return. |
| 196 | |
| 197 | |
| 198 | .. attribute:: shlex.escape |
| 199 | |
| 200 | Characters that will be considered as escape. This will be only used in POSIX |
| 201 | mode, and includes just ``'\'`` by default. |
| 202 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 203 | |
| 204 | .. attribute:: shlex.quotes |
| 205 | |
| 206 | Characters that will be considered string quotes. The token accumulates until |
| 207 | the same quote is encountered again (thus, different quote types protect each |
| 208 | other as in the shell.) By default, includes ASCII single and double quotes. |
| 209 | |
| 210 | |
| 211 | .. attribute:: shlex.escapedquotes |
| 212 | |
| 213 | Characters in :attr:`quotes` that will interpret escape characters defined in |
| 214 | :attr:`escape`. This is only used in POSIX mode, and includes just ``'"'`` by |
| 215 | default. |
| 216 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 217 | |
| 218 | .. attribute:: shlex.whitespace_split |
| 219 | |
| 220 | If ``True``, tokens will only be split in whitespaces. This is useful, for |
| 221 | example, for parsing command lines with :class:`shlex`, getting tokens in a |
| 222 | similar way to shell arguments. |
| 223 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 224 | |
| 225 | .. attribute:: shlex.infile |
| 226 | |
| 227 | The name of the current input file, as initially set at class instantiation time |
| 228 | or stacked by later source requests. It may be useful to examine this when |
| 229 | constructing error messages. |
| 230 | |
| 231 | |
| 232 | .. attribute:: shlex.instream |
| 233 | |
| 234 | The input stream from which this :class:`shlex` instance is reading characters. |
| 235 | |
| 236 | |
| 237 | .. attribute:: shlex.source |
| 238 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 239 | This attribute is ``None`` by default. If you assign a string to it, that |
| 240 | string will be recognized as a lexical-level inclusion request similar to the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 241 | ``source`` keyword in various shells. That is, the immediately following token |
| 242 | will opened as a filename and input taken from that stream until EOF, at which |
| 243 | point the :meth:`close` method of that stream will be called and the input |
| 244 | source will again become the original input stream. Source requests may be |
| 245 | stacked any number of levels deep. |
| 246 | |
| 247 | |
| 248 | .. attribute:: shlex.debug |
| 249 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 250 | If this attribute is numeric and ``1`` or more, a :class:`shlex` instance will |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 251 | print verbose progress output on its behavior. If you need to use this, you can |
| 252 | read the module source code to learn the details. |
| 253 | |
| 254 | |
| 255 | .. attribute:: shlex.lineno |
| 256 | |
| 257 | Source line number (count of newlines seen so far plus one). |
| 258 | |
| 259 | |
| 260 | .. attribute:: shlex.token |
| 261 | |
| 262 | The token buffer. It may be useful to examine this when catching exceptions. |
| 263 | |
| 264 | |
| 265 | .. attribute:: shlex.eof |
| 266 | |
| 267 | Token used to determine end of file. This will be set to the empty string |
| 268 | (``''``), in non-POSIX mode, and to ``None`` in POSIX mode. |
| 269 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 270 | |
| 271 | .. _shlex-parsing-rules: |
| 272 | |
| 273 | Parsing Rules |
| 274 | ------------- |
| 275 | |
| 276 | When operating in non-POSIX mode, :class:`shlex` will try to obey to the |
| 277 | following rules. |
| 278 | |
| 279 | * Quote characters are not recognized within words (``Do"Not"Separate`` is |
| 280 | parsed as the single word ``Do"Not"Separate``); |
| 281 | |
| 282 | * Escape characters are not recognized; |
| 283 | |
| 284 | * Enclosing characters in quotes preserve the literal value of all characters |
| 285 | within the quotes; |
| 286 | |
| 287 | * Closing quotes separate words (``"Do"Separate`` is parsed as ``"Do"`` and |
| 288 | ``Separate``); |
| 289 | |
| 290 | * If :attr:`whitespace_split` is ``False``, any character not declared to be a |
| 291 | word character, whitespace, or a quote will be returned as a single-character |
| 292 | token. If it is ``True``, :class:`shlex` will only split words in whitespaces; |
| 293 | |
| 294 | * EOF is signaled with an empty string (``''``); |
| 295 | |
| 296 | * It's not possible to parse empty strings, even if quoted. |
| 297 | |
| 298 | When operating in POSIX mode, :class:`shlex` will try to obey to the following |
| 299 | parsing rules. |
| 300 | |
| 301 | * Quotes are stripped out, and do not separate words (``"Do"Not"Separate"`` is |
| 302 | parsed as the single word ``DoNotSeparate``); |
| 303 | |
| 304 | * Non-quoted escape characters (e.g. ``'\'``) preserve the literal value of the |
| 305 | next character that follows; |
| 306 | |
| 307 | * Enclosing characters in quotes which are not part of :attr:`escapedquotes` |
| 308 | (e.g. ``"'"``) preserve the literal value of all characters within the quotes; |
| 309 | |
| 310 | * Enclosing characters in quotes which are part of :attr:`escapedquotes` (e.g. |
| 311 | ``'"'``) preserves the literal value of all characters within the quotes, with |
| 312 | the exception of the characters mentioned in :attr:`escape`. The escape |
| 313 | characters retain its special meaning only when followed by the quote in use, or |
| 314 | the escape character itself. Otherwise the escape character will be considered a |
| 315 | normal character. |
| 316 | |
| 317 | * EOF is signaled with a :const:`None` value; |
| 318 | |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 319 | * Quoted empty strings (``''``) are allowed. |